Third-person singular present tense: he, she, or it damages the reputation of; tarnishes.
From besmirch plus the -es ending (used after sibilants like -ch). Standard present tense conjugation.
The -es/-s variation in English verb conjugation follows phonetic logic—we add -es after hissing sounds (kisses, wishes, besmirches) because our mouths need that extra schwa sound to separate the sounds. It's linguistic efficiency built into our grammar.
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