Trash players are people who have the skill, talent, inflated ego, or inborn tendency to draw fire and attention. Planned or not this is very useful to a trash players team. The more people trying to hit him the less there are to hit the rest of the team. Trash players often have a interesting comment or a laugh when they shoot their opposing team. Yelling loudly, often to/at his own team, or towards the other team there is often little confusion as to where the trash player is.
A trash player may also be just about anything, thought there are few ghost style trash players. Simply because being loud doesn't help make one stealthy. Lastly good long living trash players learn how to get to the other team without hurling insults. Or at least curbing the ones they make.