From Dragon Quest Wiki

Counter is an ability introduced in Dragon Quest Monsters: Joker. For 64 MP, the user counters the next attack made against it.

Dragon Quest Monsters: Joker[edit]

Counter can be learned from:

Dragon Quest Monsters: Joker 2[edit]

Counter can be learned from all the skills it could be previously, as well as from Battle Road Master for 56 points or from Missing lynx for 60 points.