A Nebula is a type of person who is a complete dickhead, you may call someone 'A Nebula' if they are heavily queer .
This name comes from the actual definition of nebula being a cloud of dust and gas in space which is were the name comes from, as this person is usually just spouting absolute nonsense (hence the gas part) in space as no one wants to be near them.
"That guy/girl is such a nebula."
A sushiroll is an absolute unit of a gal, the wider her shoulders and the more she leaves the xbox party the more she is a sushiroll. If she plays GTA, a good way to spot if a girl is a sushiroll is when playing the gamemode deadline, will mute her mic out of anger and then is 50/50 chance of deleting you or sucking even harder.
God that girl is such a Sushiroll.