Pentuplet is an improper or slang term for quintuplet, meaning a woman giving birth to five children. Much like twins are two babies, triplets are three, quad-four, quint-five, sex-six, sept-seven, oct-eight, and so on.
In music pentuplets are note-groupings (the term polyrhythm is common) in which a note value is divided equally in 5 instead of 2. They are distinguished by a bar ("beam") over or under them with the number 5 written nearby - usually above/below or in a break in the middle of the beam.
So, there are 2 quavers (half-beats) in a crotchet usually. If one were to put a quituplet-beam over 5 quavers (usually two-and-a-half beats altogether) they become shorter so that they evenly subdivide the beat in 5.
Pentuplets, just like the shape.
Don't you mean quintuplets?
Five identical children born at the same time are referred to as pentuplets.
Penta- or Quin-. For example, a group of five babies born at the same time are called pentuplets, and an animal with five legs is called a pentaped.