Of the nature of frustration; tending to frustrate or thwart; causing disappointment or annoyance.
From 'frustrate' plus the suffix -ory or -atory (tending to, relating to). This is a rare variant formation that is even less common than 'frustrative.'
With '-ory' and '-atory,' English builds adjectives from verbs—'frustratory,' 'migratory,' 'defamatory'—this suffix makes things sound extra formal, almost legal or scientific!
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