To go face-first into the ground, or to crash in a plane nose dive. The many connotations of this slang phrase are mostly negative, save for perhaps someone into cliff diving that leaps headfirst into deep cold waters!
You can also hear this expression in old movies and competitive sports.. when a player is paid to lose
.. to hit the tarmac and stay down to the count of 10
. In a computer crash
, to take a dive, means to not return to function.