The
reverse side of a
coin from
heads. With an
American quarter, tails is the side with the
eagle, or more
recently, the side with the
state insignia. In the
UK tails is the side
without the
Queen's
head on it. On the 2p, 10p, etc., the tails is often the side with
bowers/
leaves on it.
The tails designation is used almost exclusively in coin tossing.
(thanks for the UK info, nine9)