2to suddenly announce a new charge, tax etc or say that something is not allowed - used especially when you think this is unfair:
Many tour operators slap on supplements for single people.
slap something on something
In 1977, the president slapped a ban on the commercial reprocessing of nuclear fuel.
WORD FOCUS: hit WORD FOCUS: hit with your fist:punch, thump, bash with your open hand as a punishment:smack, spank, slap with a hammer:bang, hammer in order to get attention:bang, knock, tap, hammer accidentally:bump into, crash into, strike, bang, knock, collide (with) ➔ See alsohit
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.