Dolphin brain is a metaphor for the mental connections/ train of thought made by a ND person in between conversation. It can be used to describe the thought process made mentally by a ND person in-between verbal conversation.

Imagine a dolphin jumping out of the water; that's the voiced thoughts/conversation. The dolphin then disappears in the water which is when the unvoiced thoughts happen, and the mental connections between a to z is made.

NT's only see the breach of the water which is just a faction of what is happening beneath the surface which is why confusion happen when a ND goes from talking about mango to orchids.

(Inspired from tweet by @3TrackMind79 on twitter)