def. An especially unattractive member of an otherwise good-looking group of socializing females.

Addendum: Also sometimes known as the "Fat Friend," one will observe that the Friendasaurus is sober and apparently PMSing, which aids in her dual roles of the outing; being the DD for the group, and as the Grandmaster Cockblocker, foiling any attempts for an eventual sexual encounter with one of the more attractive ladies of the group.

There is always an obligatory "fat" friend in any group of hot girls... the Friendasaurus!

When an attractive girl has a surprisingly unattractive friend that always hangs around providing a constant living cock block for all men trying to make a play.