Noun. An extremely voluminous fart which often does not have the usual tell-tale "farting noise;" but rather a large "whooshing" sound due to the unbelievable amount of gas being released. Also noteworthy for its characteristic ability to produce significant, hot breezes that can move small objects/clothing, be felt escaping the bottom of a pant leg, or can even be felt by others. Often rated in terms of typical weights in pounds for very large human babies.
Herman broke up with his girlfriend because while sleeping at night, she gave birth to a twelve pound air baby that actually moved his penis, puffed up the blankets, and was so hot that it caused him to sweat profusely.
Sherman's hot air balloon was out of fuel and quickly crashing to the ground. Luckily, he gave birth to identical twin air babies and was able to slow his descent and land safely.
When you engage in butt sex and the air gets shoved up your rectum and you get bloated to the effect of feeling pregnant.
Oh honey, you certainly did give me an air baby last night! I feel like I'm about to deliver!