Noun:
* Definition: An opening on the top of a whale's or dolphin's head through which it breathes.
* Example: The whale breached the water, its blowhole spraying a plume of water.
Verb:
* Definition: To blow out air from the mouth or nostrils.
* Example: The children were blowholing bubbles in the bathtub.
The part of speech depends on its usage in the sentence.