What does it mean to be in "Flow"?

1) Completely involved, acutely-focused, highly-concentrated - with a disappearance (or at least quieting down) of the internal peripheral incessant 'chitter-chatter'
2) Sense of ecstasy - of being outside everyday reality
3) Great inner clarity - knowing what needs to be done. Recognizing/realizing how well everything is in fact going, i.e. having gratitude for all of one's blessings vs. over-emphasizing the perceived lackings.
4) Complete compatibility between task and skill/knowledge level. Neither anxious nor bored.
5) Sense of serenity - no worries about self, feeling of growing beyond the boundaries of ego - afterwards feeling of transcending ego in ways not thought possible
6) Timelessness - thoroughly focused on present, don't notice time passing
7) Intrinsic motivation - whatever produces "flow" becomes its own reward

Desirable side effects: disappearance of self-consciousness and insecurities
Undesirable side effects: once you know this state, it makes being ok with the steady state of being scattered, distracted, and anxious that much harder.