underpart

From under- +‎ part.

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underpart (third-person singular simple present underparts, present participle underparting, simple past and past participle underparted)

1. (transitive) To divide (a part) and assign subordinate portions of it.

underpart (plural underparts)

1. A lower or underneath part.
   1. (ornithology, usually plural) Such a part of a bird.

      Hyponyms: underwings, undertail

      buffy underparts

      This bird species has tan underparts. Try to catch a glimpse when the bird takes off.

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