Definitions
1.NounAction where a player first calls, bets or raises a certain amount and then adds more. It can be used to gather weakness/strength tells from opponents before deciding how many chips to add into the pot. It is not allowed in most games. To prevent string betting, player's action is considered final as soon as the player orally states the amount they bet/raise, say for example "call" or the first chip touches the table in front of their stack/cards. One common phrasing of a string bet is, "I see your X and raise you Y."
2.NounA raise where the chips are put into play in more than one movement. Such a raise is usually illegal and counts as a call.
3.VerbTo make such a raise.