A
Digital Subscriber Line Access
Multiplexer. It is a box that sits in
leased space in the
local office of your
local telephone utility. It takes a bunch of (relatively)
puny DSL lines and
MUXes them into a
fiber pipe that gets sent up to bigger fish in the
internet pond.
If a potential job description mentions DSLAMS, you probably don't want it, because you'll have to work with phone companies, which are pretty evil.