IPA: /ˈθiːvɪʃ/
KK: /ˈθivɪʃ/
Having qualities or behaviors that are typical of a thief, often involving sneaky or dishonest actions.
The thievish behavior of the raccoon made it difficult for the campers to keep their food safe.
Comparative: more thievish
Superlative: most thievish
Thievish is formed from "thief" (from Old English "þēof", meaning a person who steals) and the suffix "-ish" (meaning having the quality of). The word "thievish" describes someone or something that has the qualities or characteristics of a thief.
Think of a 'thief' who has qualities that are 'thievish' — that's why thievish means having the characteristics of a thief.