Casual sex with a stranger. It frequently refers to casual sex between two anonymous males in public restrooms. Laud Humphreys studied it in 1960 as a doctorate student of sociology at Washington University. The University refused to grant him the PhD for ethical reasons. Conceptually, it is close to one-night-stand, and no-strings-attached sex.
Michel Foucault, the famous French philosopher, experienced impersonal sex while visiting San Francisco.