# Under-Defense

> Source: [Under-Defense in the Smarter.Poker Glossary](https://smarter.poker/glossary/under-defense)

## Definition
Under-Defense Is Folding Too Often When Facing Bets, Which Lets An Opponent Profit By Betting Any Two Cards. A Player Defending Well Below The Minimum Defense Frequency In Common Spots Is Easy To Exploit With Bluffs. The Fix Is To Continue With More Hands That Have Equity Or Blockers, Not To Call Everything.

- **Category**: Theory
- **Term Code**: `under-defense`
- **DefinedTermSet**: [Smarter.Poker Poker Glossary](https://smarter.poker/glossary)

## Related Poker Terms

- [MDF (Minimum Defense Frequency)](https://smarter.poker/glossary/mdf) ([Markdown](https://smarter.poker/glossary/mdf.md)): Minimum Defense Frequency, Or MDF, Is The Share Of Your Range You Must Continue With So That An Opponent's Bluff Cannot Profit Automatically. It Equals The Pot Divided By The Pot Plus The Bet, So Facing A Pot Sized Bet You Defend At Least Half Your Range. It Is A Guideline, Not A Rule, Against Opponents Who Rarely Bluff.
- [Exploitative Play](https://smarter.poker/glossary/exploitative-play) ([Markdown](https://smarter.poker/glossary/exploitative-play.md)): Exploitative Play Deliberately Departs From A Balanced Strategy To Win More Against A Specific Opponent's Mistakes, Such As Bluffing More Against A Player Who Folds Too Often. It Can Earn More Than Game Theory Optimal Play Against Weak Opponents, But It Opens You To Counter Exploitation If The Read Is Wrong Or The Opponent Adjusts.
- [Range](https://smarter.poker/glossary/range) ([Markdown](https://smarter.poker/glossary/range.md)): A Range Is The Full Set Of Hands A Player Could Hold In A Given Spot, Based On Their Position And Every Action So Far. Strong Players Think In Ranges Rather Than Single Hands, Because Opponents Act With Many Hands In The Same Way. Reading A Range Means Narrowing It Street By Street As New Actions Arrive.
- [Blocker](https://smarter.poker/glossary/blocker) ([Markdown](https://smarter.poker/glossary/blocker.md)): A Blocker Is A Card In Your Hand That Reduces The Number Of Combos Of A Particular Hand Your Opponent Can Hold. Holding The Ace Of Hearts On A Board With Three Hearts Means The Opponent Cannot Have The Nut Flush. Blockers Guide The Choice Of Which Hands To Bluff With And Which Marginal Hands Can Call.

## Related Strategy Lessons

- [How To Defend The Big Blind](https://smarter.poker/learn/big-blind-defense) ([Markdown](https://smarter.poker/learn/big-blind-defense.md)): Against A 2.5 Big Blind Button Open The Big Blind Needs Only 27.3% Equity To Call, And The Smarter.Poker Reference Defends By Three Betting 7.2% Of Hands And Calling 11.2%, With The Full Chart Below.
- [Minimum Defense Frequency (MDF)](https://smarter.poker/learn/minimum-defense-frequency) ([Markdown](https://smarter.poker/learn/minimum-defense-frequency.md)): Minimum Defense Frequency Is The Share Of Your Range You Must Continue With So A Bluff Cannot Profit Automatically: Against A Pot Sized Bet It Is 50%, And Against A Half Pot Bet It Is 66.7%.

## Practice On Smarter.Poker

- [GTO Training](https://smarter.poker/hub/training): Scenario Based Poker Training, Free To Play.
- [Virtual Poker Table Sandbox](https://smarter.poker/features/virtual-poker-sandbox): Interactive Multi-Street Hand And Range Scenario Explorer.

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