Frozen in place and unable to move or act, such as by the hold person spell. A paralyzed character has effective Dexterity and Strength scores of 0 and is helpless, but can take purely mental actions. A winged creature flying in the air at the time that it becomes paralyzed cannot flap its wings and falls. A paralyzed swimmer can't swim and may drown. A creature can move through a space occupied by a paralyzed creature -- ally or not. Each square occupied by a paralyzed creature, however, counts as 2 squares.
As an extraordinary or supernatural ability, this special attack renders the victim immobile. Paralysis works on the body, and a character can usually resist it with a Fortitude saving throw (the DC is given in the creature's description). Unlike hold person and similar effects, a paralysis effect does not allow a new save each round.