In a glancing manner; with a glance or brief look; indirectly or tangentially.
From glancing (present participle of glance) + -ly (adverb suffix). Captures both the physical action of glancing and the metaphorical sense of touching on something briefly.
The word brilliantly captures that oblique way things happen—a glancing blow in boxing barely connects but can still hurt, and we use this same word for ideas that touch our mind only briefly.
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