Tending to frustrate or cause frustration; characterized by or causing frustration.
From 'frustrate' plus the suffix -ive (tending to, characterized by). This is a valid adjectival form though less commonly used than the -ing form 'frustrating.'
English has 'frustrating' and 'frustrative' that mean almost the same thing, but they sound different—'frustrative' is more formal and technical, rarely used in everyday speech!
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