n. Person who accompanies two (or more) couples in a social
situation, who does
not have a partner
of his or her own. Often
the fifth person's attendance is encouraged by one of the well-meaning
but ignorant female partners, who may feel
sorry for the lonely person, but will inevitably ignore them once
the lovemaking starts. It carries the connotation that the fifth person is often
an unneccesary and unwelcome addition to the scene in these conditions. Derived from "the fifth wheel
of a car", which needing only four wheels
to run, has no need of a fifth.
"Jim and Sue, Mike and Sally invited me to come
camping with them, but I refused as I would only have been
the fifth wheel on my own!"