His thievish glance made people suspect he had stolen something.

thievish 是由名词 thief（小偷）加上形容词后缀 -ish 构成的形容词。后缀 -ish 表示"具有...特性的"，所以 thievish 意思是"像小偷一样的、鬼鬼祟祟的"。