IPA: /ˈplʌmpɪʃ/
KK: /plʌmpɪʃ/
Somewhat fat or rounded in shape.
The plumpish cat lounged on the sunny windowsill.
Plumpish is formed from "plump" (of uncertain origin, possibly from Middle English "plumpe", meaning to fall heavily or to be well-rounded) and the suffix "-ish" (meaning having the quality of or somewhat). The word "plumpish" describes something that is somewhat plump or rounded.
Think of something that is 'somewhat rounded' or 'full' — 'plump' suggests fullness, and '-ish' indicates a quality of that fullness.