Answer: Elliptical—a-lip-tickle.
More Classic Riddles with answers
Previous: What is the longest and yet the shortest thing in the world; the swiftest and yet the slowest; the most divisible and the most extended; the least valued and the most regretted; without which nothing can be done; which devours every thing, however small, and yet gives life and spirits to every object, however great?
Next: What kin is that child to it's father who is not it's father's own son?