Telegraphic

a.
  1. Of or pertaining to the telegraph; made or communicated by a telegraph; as, telegraphic signals; telegraphic art; telegraphic intelligence.
  2. having only the essential information; brief; concise; terse; -- of communications, by analogy with the style of telegrams, which are short to avoid unnecessary expense.

a telegraphic communication should have enough information to allow comprehension of the content, though it may leave out normally included words. If so much is left out that the communication becomes difficult or impossible to understand, it may be called cryptic. “Sighted sub. Sank same.” is a telegraphic message.