As a Noun: 1. The distance between the top and bottom surfaces of something. English = depth. 2. The great intensity or seriousness of a situation, emotion, thought, etc. English = depth, profundity. 3. The degree or amount to which something is serious or important. English = depth. As a Verb or Adjective: 1. To extend a long way down from the surface. English = (be) deep. 2. Of thoughts, ideas, etc., to be serious and to be about important things. English = (be) deep, (be) profound. 3. Of understand or analysis, to be very serious, exhaustive, or complete, and to show a great deal of intellectual understanding. English = (be) deep, (be) profound. As Modifier: 1. Used immediately next to a verb of communication to mean what is signed, said or written includes all of the information that is relevant to the topic. English = in detail.