Americana:
A submission where you grab your opponent's wrist with one hand, then bring your other arm underneath theirs, grabbing your own wrist in what is known as a Figure Four grip. With the opponent's elbow pointing downwards, you then use your grip to simultaneously push their wrist back and lift their elbow up and pull the arm down towards the hip. If the opponent does not escape or submit by tap, the American will break the shoulder joint.

Armbar:
juji gatame in Japanese. This is an arm lock in which the elbow joint is hyperextended.

Base:
Refers to the balance and stability as established by good foot and hand position.

Bridge: see UPA

Clinch:
A grappling fight for dominant position while standing, which often involves underhooking the opponent's arms. In Brazilian Jiu-Jitsu, the objective is generally to use a dominant position to take the opponent down.

Closed Guard:
A position in which you are on your back in a defensive position in which your legs are wrapped around your opponent. Your feet cross using the ankles and instep to create a tight hold on the opponent.

Collar Choke:
Also referred to as x-choke, lapel choke, cross choke, or jujime. The choke is accomplished by gripping the collars of your opponent with opposite hands. The choke occurs from torquing your wrists to tighten the hold, which cuts off blood suppoly of the carotid arteries, resulting in temporary loss of consciousness or "choke out."

Ezekiel Choke:
Reverse of the REAR NAKED CHOKE, using the inside of the sleeves for grip.

Figure-4:
A particular grip used for leverage. The positioning of the attackers wrists resemble a number "4". This is a grip often used when executing an armbar, wrist lock, Americana or Kimura.

Gable Grip:
A style of grip in which palms are together, fingers are not interlocked, and wrap around the hand under the thumbs.

Gi:
This is the heavy cotton pants and top worn by Jiu-Jitsu practicioners. BJJ gis are typically lighter material and tighter than Judoku gis.

The Guard:
AKA dojime and do-osae. A position where the defending person on his back has his legs wrapped around his opponent's waist, with feet interlocked. The Guard has many forms, including open, closed, half, butterfly, octopus, rubber, and others.

Guillotine:
AKA mae hadakajime. This is a powerful headlock applied by wrapping one arm under the opponent's neck, and squeezing using various biomechanics to force a submission.

Half-Guard:
AKA ashigarami. Similar to GUARD, except that in this case, only one leg has been trapped as opposed to the waist or both legs. When the defender wraps his legs around a single leg of his attacked on top, the leg cross is referred to as the "grapevine."

Kimura:
This is essentiall a reverse AMERICANA, named after Masahiko Kimura who famously used it to defeat Helio Gracie.

Mount:
AKA tate shiho gatame. Dominant position where the attacker sits on top of the defender's torso, with legs to either side, or hooked underneath the opponent. There are a number of different Mount techniques.

Omoplata:
AKA sankaku garami. This submission uses a leg to strategically lock a shoulder by twisting the arm behind the opponent's back.

Passing the Guard:
AKA hairigata. The is the process of the dominant person on top ("in the guard") is able to extract himself from the opponent's leg wrap and assume a more advantageous position like side control, scarf hold, mount or north-south.

Post:
This refers to getting base by using an extended limb to gain stability or balance in advance of a move.

Push Sweep:
A position reversal achieved by pushing on the top of the opponent's knee to flip him onto his back while on the ground.

Rear Naked Choke:
AKA hadaka jime. This quintessential and powerful choke is executed by the attacker "taking the back" of the opponent Same principle as the GUILLOTINE, but from behind the opponent as opposed to a front headlock position.

Reversal:
can be a verb - reverse. A term used to describe a movement or technique that manages to change the combatants position. For example, if you managed to SWEEP an opponent who previously had MOUNT, meaning that you ended up in their GUARD, this could be described as a reversal.

Rolling:
A term often used in BJJ and other grappling styles, which has the same meaning as 'sparring' or randori. Rolling refers to grappling on the ground in an attempt to either submit an opponent or achieve superior position.

Scarf Hold:
Also known as kesa gatame. This is a controlling position from the side in which your back is toward your opponent, one arm reaches around the head and grabs the inner thigh of one's own leg (the leg facing forward). The forward leg is threaded under the opponent's arm. The other arm firmly grips the shoulder of the opponent.

Scissor Sweep:
Also known as hasamigaeshi or possibly kanibasami. A sweep partly accomplished by applying force with a leg on either side of your opponent like a scissors.

Shrimping:
A standard escape maneuver from the bottom in which legs shift your hips to one side or the other, pushing out your posterior.

Side Control:
Also known as sidemount, cross body, and kuzure kami shiho gatame. A position in which you are on top and perpendicular to your opponent.

To be continued...