glekansa lujvo

x1 together with x2 has sex with x3

Broadly speaking, this refers to threesomes, especially the kind in which two people more or less independently are having sex with a third person at the same time. The x1 and x2 may or may not be having sex with each other (in the gletu sense). See glesi'u

In notes:

x1 (group) has sex with x2