Definition
A non-rigid, lighter-than-air aircraft that holds its shape entirely through the internal pressure of a lifting gas (typically helium) contained within its envelope. Unlike a rigid airship, a blimp has no internal framework; if the gas pressure is lost, the envelope collapses. Lift is provided by the buoyancy of the gas, and propulsion and steering are provided by engines and control surfaces mounted on a gondola attached beneath the envelope.
Plain English
A blimp is a balloon-shaped flying craft kept in shape by the gas inside it, with a small cabin hanging below where the engines, controls, and people are.
Context Anchor
Seen in lighter-than-air aircraft discussions, aircraft structure descriptions, and maintenance references for airships.
Derivation
The origin is uncertain, but a popular account traces it to British airship handlers in World War I who flicked the envelope and described the dull sound it made as a 'blimp.' The name stuck for non-rigid airships. Knowing this helps reinforce that a blimp has no internal frame — it is essentially a pressurized gas bag, which is why it makes that hollow sound.
Why Pilots Care
Blimps fall under the lighter-than-air category and have very different handling, certification, and maintenance considerations from fixed-wing or rotary-wing aircraft. A maintenance technician working on a blimp deals primarily with envelope integrity, gas pressure, and the gondola systems rather than a rigid airframe.
Analogy
A blimp is somewhat like a long, steerable balloon with a cabin and control surfaces attached. If the internal pressure is not right, the body will not hold its proper shape.
Intuition Check
Do not assume “blimp” means any airship. In FAA and maintenance use, a blimp specifically means a nonrigid airship with no rigid internal frame holding its shape.
Example Sentence 1
Before each flight, the ground crew checks the blimp's envelope pressure to make sure it remains within the limits set by the manufacturer.
Example Sentence 2
Because it has no rigid skeleton, a blimp must be hangared carefully to avoid wind damage when deflated.