When someone is busy, they use CMB whenever they want to be called back at a suitable time. Examples include texts such as CMB when free, CMB ASAP or Missed your call, CMB. It comes in handy when an individual is multitasking or they may not be able to talk at the moment but still wish to maintain communication. The shortening is time-saving, and it is particularly common with busy people, students, and all those who enjoy short and brief text messaging. It is very effective in personal and semi-formal discussions.
