(Latin: thumb [finger]; big toe)

pollex (s) (noun), pollices (pl)
1. In anatomy, the thumb; also called, first finger, digitus 1, or digitus primus: If there were a contest of strength, the normal pollex would always be the winner over the other digits (fingers) of the hand.
2. The innermost digit of the forelimb of amphibians, reptiles, birds, and mammals: The pollex is the thumb of humans and other primates.
3. Having a skeleton of phalanges, joined by hinge-like joints that provide flexion toward the palm of the hand: The pollices have two phalanges (bones) instead of three, like the other digits or fingers.
4. Etymology: Latin pollic-, pollex or digitus primus, "thumb, big toe".
pollex extensus (s) (noun) (no plural form)
A backward deviation or abnormal variation of the position of the first big and large finger of the hand: Fern had a pollex extensus or thumb which was extended longer than normal.
pollex flaxus (s) (noun) (no plural form)
The permanent flexion or bending of a joint of the thickest digit of each hand: Karl's pollex flaxus involved a deformity in the movements of the left thumb of his hand.
pollex valgus (s) (noun) (no plural form)
The abnormal deviation or slightly different position of the shortest and broadest finger toward the ulnar side (same side of the arm as the little finger) of the larger bone of the forearm: The pollex valgus indicated an unusual turning away of the thumbs from the palms of Susan's hands or toward the larger of the two long bones between the wrist and the elbow.
pollex varus (s) (noun) (no plural form)
The abnormal turning of the thumb toward the radial (smaller bone) side of the forearm: Brandon's thickest and shortest fingers were abnormally positioned more towards the pollex varus or palms of his hands than is normal with most people.
pollical (adjective) (no comparative)
A reference to or relating to the thumb: Bruce's pollical muscles were in pain from the excessive pressures he put on them at the construction site.
pollice compresso (adjective) (not comparable)
With the first thick and short digit of a person's hand folded: Interpreted to mean that if the Roman spectators wanted a losing gladiator to live, they kept their thumbs in their fists. That meant that they kept them hidden in their palms in a pollice compresso position.
pollice verso (s) (noun), pollice versos (pl)
With thumb turned.

Currently "thumbs down" is believed to be the signal by which Roman spectators condemned a vanquished gladiator to death.

The Roman custom of spectators' voting on the fate of wounded gladiators with their "thumbs up" did not mean that the downed gladiator was to be spared. In fact, it meant that the gladiator was to be killed.

Thumbs down signified "swords down" and meant that the loser was worth more to them alive than dead, and he was spared to make up for his disgrace in the next contest.

Whenever a combatant was seriously wounded, the presiding judge, or "referee", was called upon to determine whether the man should live or die, depending on how well he fought.

The judge usually went along with the mood or desire of the spectators. If they cheered, applauded, and gave the "thumbs-down" and indicated that they liked the man, he was carted off to fight another time.

If they gave him the silent "thumbs-up" treatment, his opponent was given the signal to finish him off. The corpse was then dragged off with a hook.

The misconception of "thumbs up" and "thumbs down" is probably the result of a painting.

Our misinterpretation of the thumbs-up and thumbs-down apparently came about because a French artist Léon Gérôme understood the Latin verso (turned) to mean "turned down" and so in his painting Pollice Verso (1873), he showed the death sentence with the "thumbs-down" gesture.

Apparently the painting was so popular that Gérôme's mistake became the universally accepted interpretation as we know it today.

—Compiled from statements made in It's Greek to Me!
by Michael Macrone; published by Cader Books and Harper Collins Publishers;
1991; pages 160-161.
pollicization (s) (noun), pollicizations (pl)
The plastic surgical procedure of constructing the biggest digit on the hand from the tissues that are close to it: Nathan had a surgically produced pollicization or substitution of another digit to replace his damaged thumb.

Helene had a pollicization to free the webbed thumb on her right hand.