This is the 14136th most frequent Polish word.
poślizgnąć
"Poślizgnąć" means "to slip."
Here, 'poślizgnąć' is used reflexively ('się') to describe the action of someone accidentally slipping due to a slippery surface.
Musisz uważać, aby nie poślizgnąć się na mokrej podłodze.
You have to be careful not to slip on the wet floor.
Used in the past tense ('poślizgnął'), indicating a completed action of slipping by someone on a slippery ice surface.
Poślizgnął się na lodzie i upadł.
He slipped on the ice and fell.
Here, 'poślizg' is used as a noun derived from the verb 'poślizgnąć', referring to the event of losing control ('skid') on a road.