Is chatting flirty with the opposite sex while you are in a relationship with someone considered "cheating" to you?

flirty like "oh, i wish i were your boyfriend who gets to do you whenever he wants" , or " i cannot imagine any woman not wanting you since i, as a woman, find you so sexy"... things like these

Is chatting flirty with the opposite sex while you are in a relationship with someone considered "cheating" to you?
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