Suction is a contract bridge bidding convention used to intervene over an opponent's 1NT opening.
Advancer then takes a preference by passing or bidding the remaining suit.
Optionally additional overcalls are available to show the two non-touching suit pairs in the foregoing table – namely clubs with hearts and diamonds with spades.
Suction bids can be used as pre-empts, giving a way of opening many weak hand types cheaply.
These mean forgoing the artificial 2♣ opening, so work best in a strong club context.