Ellipsis of if it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.

(simile) Idly, listlessly, or uselessly.

(simile) Synonym of swear like a trooper

(simile, vulgar) To be extremely amorous while copulating.

(simile) repetitive, but very easy.

Alternative form of slow as molasses in January

(transitive, simile) To have an extensive and penetrating understanding of (something or someone).

(US, slang) stuck; immobilized or unable to proceed

(chiefly US) An intensifier used in the same contexts as it's on, go on, and other expressions using the word on, but to express greater emphasis.

(simile) Getting along very well; being compatible; like a house on fire.