When a person no one likes enters a conversation, therefore making it awkward, a douche grenade has been dropped. Named because the person's comments affect everyone in the group, like shrapnel from a grenade.
Bob: Did you see Shaun White's Double McTwist last night?
Mark: Yeah, man. That shit was nasty.
Tom (Friend no one likes): Yo, Louie Vito's better, he just had a rough night yesterday.
Bob: Who just dropped the douche grenade?
A female douche who is usually overweight, slightly attractive when you're drunk, but completely loses their attractiveness once you're sober again. They are purely annoying and you can't stand being next to them for one minute. Almost like a douchebabe minus the hotness.
Those hippo girls are completely douche-grenades!!
Get those douche-grenades outta here!
I thought that girl was hot but when I opened my eyes I saw her for what she truly is which is a DOUCHE-GRENADE!!!