dilatant

adjective

1. dilating; expanding.
2. Physical Chemistry. exhibiting an increase in volume on being changed in shape, owing to a wider spacing between particles.
3. Petrology. (of rock) exhibiting an increase in volume owing to rearrangement and recrystallization of constituent grains.

adjective

1. tending to dilate; dilating
2. physics of, concerned with, or exhibiting dilatancy

noun

3. something, such as a catheter, that causes dilation