when a statement is made, it is someone who replies to the statement with some kind of idiotic phrase that is just a bunch of jumbled nothingness and should have not been stated at all, and after the "tubbs" does this you are to yell at him/ or her and tell them how idiotic they are and tell them to shut up, possibly even punch them.
Someone can also be called a tubbs if they have a goat. in that case u just touch the goat and make fun of him saying he hates it.
Another definition for a tubbs is someone who has not yet learned to talk to the opposite sex, so you make fun of them and tell them they talk a lot and they know what they are doing.
Ben: Scott is a Bomb
Tubbs: yep lol
Everyone: WTF SHUT UP TUBBS
Ben: OMG look at those chicks, they are fucking ug
Tubbs: yeah, lets go, we need to get back home
Everyone: OMG WTF TUBBS you fucking talk alot u homo, do u knwo what ur doing or something?