Simple past tense and past participle of yes.(verb)
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Use "yessed" in a sentence
"Margery curtseyed, and "yessed," and "very welled," with apparent submission, but though she dared not express her thoughts, it was easy to read in her ample countenance, sad suspicions relative to the honour of her noble master, and of the forlorn damsel thus thrust upon her peculiar hospitality."
"And I told you I had to postpone lunch till Thursday, and you yessed me and said you were really busy, and did I have to call you at work?"
"I listened while the chief yessed, uh-huhed, and mmmmmed."