It's a word put together from Chillin' and Relaxing. It actually means the same. If somebody should cool down you could say he or she has to relax or has to chill out. If you decide not to choose between these to, or you haven't made a decision while you already have to say the word, you say 'Chillax'.

It could also mean having a good time with your friends.

When one is experiencing extremely high levels of various emotions that may agitate another person in their company and really needs to just chill out or relax, the annoyed party in their presence can tell them to take a chillaxative, therefore rendering it appropriate for that person to fully let go and purge their stresses until they reach a serene state of calmness.

1. To chill and relax simultaneously.
2. To loosen or reduce the level of stress by employing a more relaxed and groovy outlook.

Origin: As employed by an older teenage sister (JCP) to her overly ebullient younger siblings (JEP) and (KSG).

simply a word to describe an ultimate feeling of relaxation and chilled outness

The act of Chillaxing.

Chilling and relaxing.

This is a cross between chilling and relaxing. It means to stay calm while doing those extra things that relax you.