Answer: When a particle moves along a curve rather than a straight line, then the motion of that particle is said to be curvilinear.
Some examples of curvilinear motion are as following:
Throwing of a ball in an upward direction in a curved manner.
The riding of a bicycle by the cyclist in a curved path leading to a frequent change in the direction of the motion.
Taking turns by the driver in a car – When the car makes a turn, a curved path will be followed due to the exertion of centrifugal and centripetal force on it for that given distance.