A slow irregular variable (ascribed the GCVS types L, LB and LC) is a variable star that exhibit no or very poorly defined periodicity in their slowly changing light emissions.
These stars have often been little-studied, and once more is learnt about them, they are reclassified into other categories such as semiregular variables.
Irregular variable stars were first given acronyms based on the letter "I": Ia, Ib.
The remaining irregular stars, cool slowly varying giants and supergiants of type Ib or Ic were reassigned to Lb and Lc.
[2] When the General Catalogue of Variable Stars standardised its acronyms to be all uppercase, the codes LB and LC were used.