(chiefly music, language learning) To play (an instrument) or sing or to learn music without reading or memorizing sheet music; to learn a language without instruction. / To do by guessing, to improvise.

(transitive, obsolete) To have sex with. / (intransitive, dated) To rest from labour; to take a break.

plural of by-product

By the force of; by means of. / (by extension) Because of; by reason of.

Any of several desserts largely consisting of a chocolate cake with a chocolate sauce.

(idiomatic) According to one's understanding.

Separate and distinct from others of the same kind; treated individually.

(mathematics, logic) Proof of a statement adduced by deriving a contradiction from the statement's negation.

By a very small distance.

(UK, New Zealand) minced oath for by God.