1) sketchup is when a sketchy guy chats you up
2) a situation in which something happens that makes a sketchy situation sketchier. as in, the situation was sketched up
1) "hey girl sorry i was up in your grill dancing and taking pictures without your permission last night "yeah man you were hella sketchup"
2) "that creeper that came to the party late last night made it totally sketchup.