ADJ. A description of a person on twitter, most likely a guy, who gives you an assist ReTweeting your tweet that garners you lots of @ replies.
@Billy: (Posts a tweet)
@BillysFriend: (RT's the tweet)
(Lots of RT's are made because @BillysFriend RT'ed the tweet)
@Billy: Thanks @BillysFriend you're an awesome Twingman.
@BillysFriend: You're most welcome.