Analdew is dew on your anus leftover over from last night. Remnants of the cute guy at the bar last night on your bung hole. Morning after residue, if you will.
Dude did you get some last night? Your analdew is showing through your pants.
When you are trying to have gentle anal, but your sex partner plows his horse cock up in there, disregarding your desires and your sensitive anus.
Mom: "How was your gay sex with Timothy last night? Was it pleasant?"
Me: "It was quite painful actually. I got analated. Timothy rammed his third leg between my tight ass cheeks when I was hoping for soft sex. He aggressively entered my anal cavity."