A rotating magnetized neutron star that produces regular pulses of radiation when observed from a distance. A pulse is produced every time the rotation brings the magnetic pole region of the neutron star into view. In this way the pulsar acts much as a light house does, sweeping a beam of radiation through space.
A Pulsar Glitch is a sudden change in the pulsar period due to a sudden shift in the crust of the neutron star (a "starquake").
A Millisecond Pulsar is, as the name implies, a pulsar with a period measured in terms of milliseconds (thousandths of a second). The shortest such pulsar periods are about one and two milliseconds. Millisecond pulsar periods are very constant. They don't slow down much implying a weak magnetic field. Most millisecond pulsars are found in binary systems. It is believed that millisecond pulsars are old pulsars that have had their spin rates increased through the accretion of angular momentum-containing matter from the other star in the binary. Mass transfer has spun up these pulsars back to very fast spin rates. The idea that the millisecond pulsars are actually old systems gains support from the presence of millisecond pulsars in globular clusters.