the first impression is basically a thumb print (using your thumb to massage/penetrate a woman's anus) with a little spice added, stealthily slipping an ecstasy tab in with the thumb, to increase the sexual experience for the woman
"Damn Brian, that sex was amazing, thanks for that First Impression"
How you present yourself in the meeting of a new person.
Most people look back on these and wish they'd made a better one.
"Jesus fucking Christ, Kate, you should've told me your parents would be there. I would have worn more suitable clothes to give them a good first impression... You really fucked up my evening."