The Collaborative International Dictionary of English v.0.48:
Nonsense \Non"sense\, n. [Pref. non- + sense: cf. F. nonsens.]
1. That which is not sense, or has no sense; words, or
language, which have no meaning, or which convey no
intelligible ideas; absurdity.
2. Trifles; things of no importance.
Nonsense verses, lines made by taking any words which
occur, but especially certain words which it is desired to
recollect, and arranging them without reference to
anything but the measure, so that the rhythm of the lines
may aid in recalling the remembrance of the words.
Syn: Folly; silliness; absurdity; trash; balderdash.