The Collaborative International Dictionary of English v.0.48:

Momental \Mo*men"tal\, a. [Cf. OF. momental.] [Obs.]
   1. Lasting but a moment; brief.
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            Not one momental minute doth she swerve. --Breton.
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   2. Important; momentous.
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   3. (Mech.) Of or pertaining to moment or momentum.
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