in a manner that makes something worse or is deeply frustrating and annoying.
From 'aggravate' plus '-ing' (present participle) plus '-ly' (adverb suffix). Creates an adverb describing the manner of aggravation.
Adding '-ingly' to adjectives is one of English's most productive word-making patterns—you can almost certainly understand 'aggravatingly' even if you've never heard it before, which shows how predictable our grammar patterns are.
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