animation quality drop; poorly drawn episode; art inconsistency
Slang used by anime/manga fans when an episode or scene has noticeably worse art than the rest of the series, or when the animation is consistently bad.
This week's episode had really bad art, didn't it?
That anime started showing noticeable art decline from the second half.
Compound of 作画 (drawing, artwork) and 崩壊 (collapse, breakdown). Originated in online anime fan communities to describe episodes with noticeably poor or inconsistent animation quality.