a bag that fills with air
"The swimmer inflated her bladder to float on the surface of the water."
A flexible sac that can expand and contract and that holds liquids or gases.
"The swimmer's bladder expanded to help her float on the surface of the water."
In plain English: The bladder is a small, stretchy bag inside your body that holds urine until you go to pee.
"I need to take a break from work because my bladder is full."
Usage: The noun refers primarily to the body organ that stores urine, while the verb describes something swelling up as if filled with gas. Use this word for biological storage functions rather than general containers, which are better described by terms like "bladder" in slang or specific industrial contexts only when mimicking expansion.
To swell out like a bladder with air; to inflate.
"The sunflower seeds began to pop and swell in their shells until they were as big as tiny bladders."
In plain English: To bladder means to fill your urinary tract with urine until you need to go pee, though this word is rarely used as a verb and people usually just say they have an urge to urinate instead.
"The old man had to stop at every gas station because he couldn't hold his bladder for long."
The word "bladder" comes from Old English and originally meant both a blister on the skin and an animal's urinary sac. It traveled into Middle English with this dual meaning before settling on its current sense of referring specifically to the body organ or storage bag.