implied threat

In THE BOOK OF BLUFFS, Matt Lessinger defines "the implied threat" as:
"When attempting a bluff before the river, your opponent understands that he must not only consider your current bet, but the possibility of future bets as well. While he might consider calling your current bet, it's the implied threat of future bets that might discourage him from calling."

This is an important concept, and Lessinger states it well and explains it more fully in his book. If you hold a medium strength hand or a vulnerable hand, ask yourself, how much will it cost me to get to the showdown. While the pot odds might be correct for you to call on the flop, if you factor in the turn and river bets, you might be best served by folding early.