buy in

(to something)

1. Lit. to purchase shares of something; to buy a part of something the ownership of which is shared with other owners. I bought into a company that makes dog food. Sounds like a good company. I would like to buy in.

2. Fig. to agree with; to accept an idea as worthwhile. The committee liked my proposal and decided to buy into my plan. Do you think you can get the whole board to buy in?