used in chat/AIM slang as a way to denote that the other person has just received a minor slap to the back of the head, like what Leroy Jethro Gibbs gives his team.

The slap is a punishment, usually done when the person has done/said something stupid.

Can be used as an expression of aggravation

To smack someone on the back of the head with an open hand. Derived from the trademark slap delivered by the character Leroy Jethro Gibbs to his underlings on the T.V. show N.C.I.S. To deserve a 'gibbs' or a 'gibbs-smack' the person getting it should have done something stupid, vain or dangerous.

Former marine gunnery seargent,Leroy Jethro Gibbs, the main character on the hit tv show NCIS, played by Mark Harmon.

also known as "Bossman", "Boss", and "Silver Fox".

aka: the most amazing man to ever grace the world with his presence.

To roll. Any form of the word roll can be used in this context.

a legendary god who pleasures females until ecstasy with his large penis

(also has 12 testes)

Gibbs’s are very intelligent and talented and understand human emotions. They make good grades in m school and they do many things that are constructive

These people have many friends and are funny and is a nice person to hang around with.
Gibbs’s can be annoying with personal issues and talk too much.
They are also very overprotective but rarely display their emotions . Also they are slow to anger which means they don’t get mad easily. These people do not take a lot of things seriously.
Gibbs’s are either short or very tall. They are not the best looking people on the planet but they are a good catch because they deeply care about the ones they love and they think about their future a lot.
Gibbs’s are very complex with their emotions because they have many different personalities.