[T] to prevent someone from doing somethingIf she really wants to leave, I don't understand what's stopping her.
[+ -ing verb] They've put barriers up to stop people (from) getting through.
Something must be done to stop the fighting.
stop a cheque UK (US stop payment on a check) to tell your bank not to deal with a cheque which you have written, so that the money is not paid from your bank account