two dots placed side by side after a note to indicate that it is to be lengthened by three quarters of its value.
verb
(double-dot) [with object] write or perform (music) with a rhythm of alternating long and short notes in a ratio of seven to one, producing a more marked effect than ordinary dotted rhythm: (as noun double-dotting)some may feel at times that the double-dotting is being a little overdone
double dot in other Oxford dictionaries
Definition of double dot in the US English dictionary
