Similar to chill
, meaning relax, but also with a subtle vituperative connotation. Espesially used in situations where no defininte answer can be given; AND one wishes to very tacitly put down the answer seeker through the inappropriate assertion that one is another's "son" and therefor, subordinate.
A friend asks his mate, "When will we be departing for the theatre this evening?" After a few moments of unfruitful thought, the friend recieves an irate response of, "Chill son" from his mate.