The Collaborative International Dictionary of English v.0.48:
gasbag \gasbag\ n. 1. a person who talks a great deal about uninteresting topics. Syn: windbag. [WordNet 1.5] 2. the bag containing the gas in a balloon. Syn: envelope. [WordNet 1.5]WordNet (r) 3.0 (2006):
gasbag n 1: a boring person who talks a great deal about uninteresting topics [syn: gasbag, windbag] 2: the bag containing the gas in a balloon [syn: envelope, gasbag]