Late 18th-century Dutch painting of a baby asleep in its mother's lap
A lap is a surface created between the knee and hips of a biped when it is in a seated or lying down position.
A lap is also to complete a single circuit of a race track, or two lengths of a swimming pool or similar. Used as a verb, to lap is to overtake someone in a race by a full circuit (i.e. to have completed an extra lap than them).