In a gluey manner; in a way that is sticky, adhesive, or having the quality of glue.
From 'gluey' (adjective) plus the adverbial suffix '-ly,' which converts adjectives into adverbs describing how something is done or appears.
The adverb 'gluily' is rarely used because it sounds awkward—we'd typically say 'in a sticky way' instead—which shows that not all grammatically valid words are actually used; English speakers unconsciously avoid creating adverbs from certain adjectives.
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