Definition of opposable in English:

opposable

adjective

Zoology
  • (of the thumb of a primate) capable of moving toward and touching the other digits on the same hand.

    • ‘A panda with a fully opposable thumb that is lacking in its nearest relatives is hard to explain via evolution.’
    • ‘Their hands had only three digits: two fingers and an opposable thumb.’
    • ‘The first 2 digits of their forefeet are opposable to the other three in the more arboreal species.’
    • ‘Digits 1 and 2 on the forefeet are opposable to digits 3-5, and the hindfoot has a well-developed hallux.’
    • ‘In other words, our ancestral rodents did not merely evolve gradually until they emerged as bipeds with opposable thumbs.’

Pronunciation:

opposable

/əˈpōzəbəl/