n.1 a (often as int.) absurd or meaningless words or ideas; foolish or extravagant conduct. b an instance of this.
2 a scheme, arrangement, etc., that one disapproves of.
3 (often attrib.) a form of literature meant to amuse by absurdity (nonsense verse).
Derivatives:
nonsensical adj. nonsensicality n. (pl. -ies). nonsensically adv.