In vain; useless; serving no purpose; futile in its effects.
From Latin 'frustra' (in vain) plus the suffix -neous. This is an archaic or rare English adjective that combines the Latin root with a productive English suffix.
This word shows that English borrowed not just Latin words but also Latin patterns—we attached '-neous' to create an adjective from 'frustra,' much like we make 'instantaneous' or 'spontaneous'!
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