To bark sharply and repeatedly, usually in an annoying way; or the sharp bark itself.
Likely onomatopoeia (imitating a sound), similar to 'yip' and 'yep.' May be influenced by Yiddish or Dutch origins, but the sound itself drives the meaning.
Yap is pure onomatopoeia—the word sounds like what it means, which is why small dogs everywhere seem to yap regardless of their breed or nationality.
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