What term indicates physical swelling due to fluids or gas?

The term that best indicates physical swelling due to fluids or gas is tumid. This word directly expresses the condition of being swollen, often used in medical or anatomical contexts where parts of the body may become engorged with fluid or expand due to other causes. Tumid captures both the literal swelling and the visual implication of an area that appears bulging or inflated.

While the other terms may have their own meanings, they do not specifically refer to swelling caused by fluids or gas. Turgid also relates to swelling, particularly in botanical contexts describing plants swollen with water, but it's less commonly used in direct reference to physical conditions in living organisms. Virago refers to a strong, assertive woman, often with a negative connotation, and does not relate to physical swelling at all. Welter describes a state of confusion or a mixture of disorganized things, which also does not pertain to the condition of swelling. Therefore, tumid is the most accurate choice for indicating physical swelling due to fluids or gas.