Requiring real thought or significant computing power. Often used as an understated way of saying that a problem is quite difficult or impractical, or even entirely unsolvable ("Proving P=NP is nontrivial"). The preferred emphatic form is "decidedly nontrivial".
See uninteresting, interesting.
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Nearby terms: non parity « non-polynomial « Non Return to Zero Inverted « nontrivial » Non-Uniform Memory Access » non-uniform quantising logarithmic compression » Non-Uniform Rational B Spline