Here is a review of the so-called “garbage stayman” convention, used to show a weak major suited hand opposite a 1NT opening.
Garbage Stayman is a 2♣ bid made by a responder to a 1NT (not 2NT) opening bid with a weak 4+/4+ major suit hand with the intention to pass if opener bids his 4-card major. Responder will typically have less than 9 high card points.
The gamble responder is making is that the NT opener has a 4 card major, but even if s/he doesn’t, a 7-card major suit fit will play better than 1NT.
If the opening notrump bidder bids 2 of a major, responder passes gratefully. If opener bids 2♦, denying a 4-card major, responder bids 2♥ which shows the weak garbage stayman hand. With 3 hearts, opener passes, comfortable that the partnership is in at least a 4-3 major suit fit; with 2 hearts and 3 spades; opener corrects to 2♠, again comfortable that the partnership is in at least a 4-3 major suit fit.