Usage patterns
気合で〈動詞〉to do something through sheer force of spirit/willpower
I got through the tough practice on sheer willpower.
〈人〉が気合を発するfor someone to let out a kiai shout while performing a technique
The athlete let out a kiai shout as he executed the move.
気合の入った〈物〉something done with real spirit and energy
The audience was amazed by the spirited, all-out performance.
気合を出すto muster up one's fighting spirit
It's almost over, so let's dig deep and push through.
Expressions
気合が入るget fired up; get motivated; get into it 気合を入れるfire oneself up; get psyched; motivate oneself · fire someone up; rouse someone