What is a tumbler?

1: one that tumbles: as a: one who performs tumbling feats : acrobat b: any of various domestic pigeons that tumble or somersault backward in flight or on the ground

2: a drinking glass without foot or stem and originally with pointed or convex base

3 a: a movable obstruction in a lock (as a lever, latch, wheel, slide, or pin) that must be adjusted to a particular position (as by a key) before the bolt can be thrown b: a piece on which the mainspring acts in a gun's lock

4: a device or mechanism for tumbling (as a revolving cage in which clothes are dried)

5: a worker who operates a tumbler
http://www.m-w.com/dictionary/tumbler

Here in the US I think we use it fitting the 2nd definition (a drinking glass) most commonly.

A tumbler can also be...
a type of pigeon that can do backward somersaults,
a larval mosquito,
a button on a chess clock
http://www.onelook.com/?w=tumbler&1s=a

Incidentally, Tumbler has also been a nickname of President G W Bush.

Tumblers are fairly common in New York City rooftop coops.
They are interesting to watch in flight.

Can be seen here (poorly) at 1:30 in.

http://www.youtube.com/watch?v=-yiJwcu3Ckg


Can be seen here quite Grandly! (they are more commonly called "Rollers".

http://www.youtube.com/watch?v=WGwDOzpTcgs

Does a tumbler have to be made of glass - is it a tumbler if it is plastic (e.g. a kid's drinking cup)?