teach / tēch/ • v. (past taught / tôt/ ) [tr.] show or explain to (someone) how to do something: she taught him to read he taught me how to ride a bike. ∎ [tr.] give information about or instruction in (a subject or skill): he came one day each week to teach painting | she teaches me French. ∎ [intr.] give such instruction professionally: she teaches at the local high school. ∎ [tr.] encourage someone to accept (something) as a fact or principle: the philosophy teaches self-control. ∎ cause (someone) to learn or understand something: she'd been taught that it paid to be passive. ∎ induce (someone) by example or punishment to do or not to do something: my upbringing taught me never to be disrespectful to elders. ∎ inf. make (someone) less inclined to do something: “I'll teach you to mess with young girls!”• n. inf. a teacher.PHRASES: teach someone a lessonsee lesson.teach school be a schoolteacher.
you can't teach an old dog new tricks proverbial saying, mid 16th century; meaning that someone who is already set in their ways is not able to learn new ways of doing things.