The lowest safe altitude or (LSALT) is used to describe the altitude at which their might be conflicting terrain within a certain radius. It is the pilot in command's responsibility to study the LSALT areas on their charts before departure and to allow a 'minimum' of AGL (Above Ground Level) or (if over any populated area).
Due care must be taken whilst flying in IMC with respect to LSALT. Descent below the lowest safe altitude can only be made
§ When necessary during climb after departure from an aerodrome.