noun
baboon
Refers to the primate. Usually written in katakana as ヒヒ.
動物園でヒヒの群れを見た。
I saw a troop of baboons at the zoo.
noun
lecher; dirty old man; skirt-chaser
Derogatory slang comparing a lecherous man to a baboon. Strongly pejorative.
あのヒヒ親父、また若い子にちょっかい出してる。
That dirty old man is hitting on young girls again.
Kanji spelling without the iteration mark; equally rare and not recommended for learners.
The word is native Japanese, likely imitative of the animal's cry. The kanji 狒 are Chinese characters for baboon, used here as jukujikun for the native word.