look up any word, like ratchet:
 
1.
Someone who has been scheduled for a fuck.
"You busy tonight?"

"Yeah sorry. I've penciled in Kristin for an hour before work."

"Cool. That chick is a total freak."

"Yup, yup."
by pH Balance January 24, 2008
 
2.
1) to have a temporary plan to do something with someone.

2) to insert your penis into a butt and/or vagina.
1) "Your appointment is penciled in for 7:00."

2) "I was penciled in with Sarah last night."
by awkbitch July 02, 2013