To go and murder someone, the "white chalk" referring to the white chalk outline that is left at a crime scene by investigators after someone is murdered and the body is removed.
The practice of leaving coded chalk marks on or near buildings or sites where a "war driver" has identified available 802.11 wireless network access. The marks usually indicate the type of access and level of security.
This practice is decended from the way hobos used to chalk mark the curbs outside homes where an easy mark could be approached for food or other handouts.
At the start of intercourse you rub the tip of your penis on the women's vagina. Also spitting on it or licking fingers and rubbing on the tip to add moisture.
I was chalking it about to nail her and she stopped me andasked what her name was.