flake 1 
(flāk)
(flāk)n.
1. A flat thin piece or layer; a chip.
2. Archaeology A stone fragment removed from a core or from another flake by percussion or pressure, serving as a preform or as a tool or blade itself.
3. A small piece; a bit.
4. A small crystalline bit of snow.
5. Slang
a. One who is undependable, as in keeping social engagements.
b. A somewhat eccentric person; an oddball.
6. Slang Cocaine.
v. flaked, flak·ing, flakes
v.tr.
1. To remove a flake or flakes from; chip.
2. To cover, mark, or overlay with or as if with flakes.
3. To lay out (a rope or sail, for example) in loose folds.
v.intr.
Phrasal Verb: 1. To come off in flat thin pieces or layers.
2. Slang
a. To renege, as on a social engagement: promised to go to the party but flaked at the last moment.
b. To fall asleep or collapse from fatigue or exhaustion: got home and flaked on the sofa.
flake out Slang
1. To renege, as on a social engagement: Sorry for flaking out on you last night—I had to work late.
2. To lose interest or nerve: I toyed with the idea of getting a tattoo but flaked out when I saw the needle.
3. To fall asleep or collapse from fatigue or exhaustion: On arriving at the campsite, we dropped our packs and flaked out on the ground.
4. To act in an odd or eccentric manner: Don't embarrass me by flaking out in front of my friends!
[Middle English; see plāk-1 in the Appendix of Indo-European roots.]
flaker n.