In the
context of
computers,
interpretation (or sometimes
recompilation) of
machine code from
another platform.
Some
warez idiots think of emulation as only good for
game console ROM emulation. However, emulation is used for many great, non-gaming, and perfectly
legal things. Such an
implementation is
demonstrated in
vmware (though that's mostly
native execution), the
Crusoe processor, the
Pentium's
RISC core, and
PowerPC Macintoshes.
Another simpler definition I've seen for emulation in
computers is simply making a
device act as
another. Example: the "
SCSI Emulation"
feature in
Linux will make an
ATAPI device use a
SCSI interface.