What does SLBM stand for?

Sea - or Submarine or Surface-Launched Ballistic Missile - Navy (CAAL)

Ship-Launched Ballistic Missile (SAUS)

Space-Launched Ballistic Missile (IAA)

Sub-Launched Ballistic Missile - Military technology (DDF)

Submarine Launched Ballistic Missile - Navy

Surface Launched Ballistic Missile - Air Force