rain check

noun6

1. •
   A reissue, at no extra charge, of a ticket for a baseball game or other outdoor event postponed or interrupted because of rain.

   • With trembling fingers he pulled out his watch. The hands pointed to five minutes to three. A blessed vision came to him of a moist and disappointed crowd receiving rain-checks up at the Polo Grounds. — 1920
2. •
   (figurative) In social interactions, a deferred invitation, or deferred acceptance of an invitation.

   • I can't go with you to the museum this Saturday, but can I take a rain check and go some other day?
3. •
   An agreement to honor a current offer after its normal expiration.
4. •
   A promise or voucher from a merchant to a customer.
5. •
   A (special) price guarantee for a sold-out item or temporarily unavailable service.
6. •
   The promise to make good on any experience that the customer deems unsatisfactory.