Noob

The word "Noob" is a word used on the Internet which descends from Newbie, which is someone who is new to a game. On ROBLOX, "Noob" is used to describe someone who engages in activities that break ROBLOX rules or are doing things that are offensive/annoying/frustrating to other users, i.e. killing people on their own team, deleting others' creations.

Looks
The stereotypical Noob is either one of two things:
 * 1) A player with a blue Torso, yellow Head and Arms, and green Legs. They sometimes have the R shirt. A variation of this may be a stone grey torso.
 * 2) A Guest

Modern Day Usage of "noob"
People call others noob due to spawnkilling, spamming, scamming. Some people get frustrated and use the word noob in a form of not "newbie" but annoying.

This is now very inevitable due to large amounts of new users coming flooding in ROBLOX, but most of them are not noobs.

Most of the time, you should not say people "noob" because they will get hurt and it is a harrassment.