Merriam-Webster Collegiate Dictionary - involute

 I. adjective  Etymology: Latin involutus concealed, from past participle of involvere  Date: 1661  1.  a. curled spirally  b.  (1) curled or curved inward  (2) having the edges rolled over the upper surface toward the midrib an ~ leaf  c. having the form of an ~ a gear with ~ teeth  2. involved, intricate  II. noun  Date: circa 1796 a curve traced by a point on a thread kept taut as it is unwound from another curve ~ of a circle  III. intransitive verb  (-luted; -luting)  Date: 1816  1. to become ~  2.  a. to return to a former condition  b. to become cleared up ; disappear