Incessant talker (10)
(Other definitions for gasbag that I've seen before include "One talks at length on boring topics" , "Person who talks too much - or a balloon" , "Loudmouth - or balloon?" , "goes on and on" , "Garrulous type" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">incessant talker</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for motormouth that I've seen before include "Non-stop chatterbox" , "Someone who won't shut up" , "Constant talker" .)