1 : a period of time when workers stop work in order to force an employer to agree to their demands
a teachers' strike
a strike by airline pilots
The workers are on strike.
Workers are threatening to go (out) on strike. = (Brit) Workers are threatening to come out on strike.
Workers threatened to take strike action.
2 [count] : a military attack
The allies have launched several strikes.
an air strike [=an attack by aircraft]
3 [count] : the act of hitting something with force
The forest fire was caused by a lightning strike. [=was caused when something on the ground was hit/struck by lightning]