Third-person singular simple present indicative form of dull.(verb)
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Use "dulls" in a sentence
"Choice, in other words, dulls the critical faculties."
"On the occasions in which I suspect that my presence on a ToC is because the story was the best of the non-WASPs, I just feel like I didn't deserve it, which kind of dulls the acceptance-dance a bit."
"Bitter and base associations have become the sole food of your memory: you wander here and there, seeking rest in exile: happiness in pleasure -- I mean in heartless, sensual pleasure -- such as dulls intellect and blights feeling."