The disorder whereby a girl may be calm and fun to talk to one day, and be an utter bitch the next day. Acts of kindness include offers of help and general pleasantness, while acts of bitchiness may include apparent constant ragging and hurling sharp objects.
The mood of which may be shown as a pattern of two bitchy days and one good day.
Named after the victim of the first recognized case: Jannika.

A Bloomer is someone with a bright outlook on life who is optimistic in nature. Bloomer's frolic in every opportunity to be happy and try to make the most out of life. The opposite of a Bloomer is a Doomer. The term Bloomer originated specifically as a counter to the Doomer on sites especially like 4Chan.