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"to make thin, to make less," 1520s, from Latin attenuatus "enfeebled, weak," past participle of attenuare "to make thin, lessen, diminish," from ad- "to" (see ad-) + tenuare "make thin," from tenuis "thin" (see tenet). Related: Attenuated; attenuating. Earlier was Middle English attenuen "to make thin (in consistency)," early 15c.
attenuate at·ten·u·ate (ə-těn'yōō-āt')
v. at·ten·u·at·ed, at·ten·u·at·ing, at·ten·u·ates
To reduce in force, value, amount, or degree; weaken; diminish.
To make bacteria or viruses less virulent.