It's when you've been trying to sleep with solid-packed sinuses which necessitates you breathing through your mouth all night. After what seems like forever trying to survive all night long, propped up, breathing through your now dry-parched and sore mouth and throat, you get up with Covid-breath which is so bad it could strip the walls of wallpaper, stop a charging rhino in its tracks and back off a zombie in mid-stride. Covid-breath is soon relieved when your cold starts breaking up and you finally start hacking up egg-sized chunks of green phlegm.
"Ugh...I had to breath through my mouth all night..," you say to your spouse as she wakes up beside you.

"Ack!" she struggles to utter. "I can tell (hack, cough). Covid-breath! Back off you foul beast! Back off or I shall be forced to slay you!!!"
by Captain Loloch February 5, 2022
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