Green’s Dictionary of Slang

1. an unpleasant or ugly person.

1987		Public Enemy ‘Miuzi Weighs a Ton’ [lyrics] You know the ducks used to criticize my every phase of rapture.
1992		D. Burke Street Talk 2 37: She used ta be a real duck but now she’s too cold!

2. (US campus) a silly person.

1987

Eble Campus Sl. Oct. 2: duck – someone who is acting really stupid.