To jack (steal) someone elses expression(s). The person who always Jack-spressions is usually too lame to come up with their own expression.
Emily told Leah and Moe that she was crushing on Conan O'brien. Leah squinched her nose and formed and O with her lips. Moe Jack-spression(ed) and repeated the same reaction.
When multiple males who fornicating with one female (or male) at the same time, (A.K.A- "running a train") , frequently alternate the usage of one condom amongst themselves.
me: Dude me and the crew ran a train on Perla last night!
Dew: Dirty Perla?
me: Yea!
Dew: Gross! Did all of you have condoms?
me: Na
Dew: Were you guys jack wrapping?
me: Hell yea!
Dew: Sweeeet....