Martial trance

From DwarfFortressWiki

When a single dwarf is being attacked by more than one enemy, it may fall into a Martial Trance and supposedly focus better. They will also actively seek fights with enemies and neutral creatures. The symbol for a dwarf in a trance is ! which will flash over his icon.

Toady has stated here [1] that trances improve most combat modifiers except direct damage.

Only creatures with the [TRANCES] flag set in their data file will enter trances. Only dwarves have this flag as default.