1to suddenly attack someone, using physical violence or unpleasant words [= turn on]
2if a situation, event, argument etc turns upon a particular thing or idea, it depends on that thing [= turn on]:
The court case turned upon a technicality of company law.
WORD CHOICE: WORD CHOICE: become, get, go, turn, grow, comebecomecan be followed by an adjective or noun, not a verb• Her husband became jealous. • We soon became friends.The following words are used with an adjective instead of become, in certain cases:get is very often used instead of become, and is more usual in spoken English• I was getting hungry. • Things got worse and worse.go is usedto say that something changes colour• The sky went pink.to say that someone feels a change in their body• My fingers have gone numb. with blind and deaf• He went blind. with mad, insane, crazyetc• The crowd went wild.turnis used especially to say that something changes colour• The liquid turned green.• His face turned pale.growcan be used in fairly literary written English to say that something changes gradually• It grew dark as we walked.with a to-infinitive, to say that someone gradually starts doing something• We grew to love each other.come is usedwith adjectives like apart, undone, and unstuck• Your shoelace has come undone.• A few pages came loose. with true• Her prediction came true. with a to-infinitive to say that someone starts doing something• I eventually came to realize (NOT became to realize) I was wrong. ➔ See alsobecome
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.