1.VerbTo request or accept a rain check (an agreement from a merchant to honor a special offer, temporarily unavailable, after the expiration date).
2.VerbIn social interactions, to request a deferred invitation, as a polite way to turn down an engagement, usually with the implication that one is simply postponing it and another time might be acceptable.
"I can't go with you to the museum this Saturday, but can I take a rain check?"