Thievish means like a thief, or inclined to steal. The -ish ending is doing the work you already know from 'childish' and 'foolish': it says the thing has the quality of a thief without necessarily being one. So a thievish look is the shifty, sideways look of someone about to take something; a thievish cat is a cat with a habit of stealing food off the table; a thievish servant is one you suspect of dipping into the money. It is a rare and old-fashioned word. You will find it in older novels and in deliberately literary writing, and almost never in conversation — a modern speaker would say 'sneaky', or just 'he steals things'. That rarity is itself the useful fact about it: when a writer chooses 'thievish' today, they are reaching for an old-book flavour on purpose. There is a second, softer use worth knowing, because it is where the word still feels alive: describing manner rather than crime. 'A thievish glance', 'thievish fingers' — here nobody has stolen anything, and the word only means 'furtive, secret, like someone who does not want to be seen'.

有賊性的、賊頭賊腦的；也可形容神情鬼鬼祟祟。屬於舊式書面語，日常會話幾乎不用。