In the context of stock plans, this is a provision in a grant agreement that makes your equity award contingent on your refraining from a specified action. This type of provision may involve, for example:

• confidentiality about company secrets
• nonsolicitation of employees after you leave the company
• noncompete forfeiture clauses

At the website of the SEC, you can see an example of a stock grant agreement that includes a restrictive covenant (see Section 2.2). For details about these provisions in grant agreements, see the related article on this website.