Definition of "cittern"

This discourse took us much time, till it was time to go to bed; but we being merry, we bade my Lady goodnight, and intended to have gone to the Post-house to drink, and hear a pretty girl play of the cittern (and indeed we should have lain there, but by a mistake we did not), but it was late, and we could not hear her, and the guard came to examine what we were; so we returned to our Inn and to bed, the page and I in one bed, and the two captains in another, all in one chamber, where we had very good mirth with our most abominable lodging.

1661 January 17, Samuel Pepys, Diary of Samuel Pepys: January 1661

The cittern consisted of a pear-shaped body similar to that of the lute but with a flat back and sound-board joined by ribs. The neck was provided with a fretted fingerboard; the head was curved and surmounted by a grotesque head of a woman or of an animal.

1911, Cittern, article in Encyclopædia Britannica Eleventh Edition

The advent of the Spanish guitar in England led to the wane in the popularity of the cittern, also known at that time in contradistinction as the English or wire-strung guitar, although the two instruments differed in many particulars.

1911, “Guitar”, in Encyclopædia Britannica Eleventh Edition

Antwerp was world-famous for its harpsichords, but it was also a centre, in the 16th century, where citterns, lutes, viols and later violins were constructed with skill.

2000, Musical Instruments Museum, Visitor's Guide‎, page 93