1. complication: an act of making something complicated or intricate, or the condition of being complicated or intricate
2. something complex: something complicated or intricate
3. involute part: an involute part or structure
4. physiology decline in function: a decline or degeneration in the physiological function of an organ
5. physiology decrease in size: a return to normal size of a body or body part after expansion
6. mathematics raising of quantity to power: the algebraic operation of raising a number, variable, or expression to a specified positive integral power, xn. See also evolution (sense 6)
7. grammar complex grammatical structure: a complicated grammatical construction
8. biology developmental process forming tube: the process by which some cells grow inward over the edge of an organ or part until they rejoin the structure to form a tube. The bladder is formed by involution.