to buy and sell a particular product; to include sb in an activity
deal in sth
to buy and sell a particular product
The company deals in computer software.
deal in sth
to accept sth as a basis for your decisions, attitudes or actions
We don't deal in rumours or guesswork.
deal sb ininformalAmerican
to include sb in an activity
That sounds great. Deal me in!
Definitions from the Oxford Advanced Learner's Dictionary, 9th edition