plectrum

n. small piece of plastic or metal used to pluck strings on musical instruments, pick, small piece of metal or plastic with which a stringed instrument may be played

A plectrum is a small flat tool used to pluck or strum a stringed instrument. For guitars and similar instruments, the plectrum (or 'pick') is a separate tool held in the player's hand. In harpsichords, the plectra are attached to the harpsichord's jack mechanism.
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Noun
1. a small thin device (of metal or plastic or ivory) used to pluck a stringed instrument
(synonym) pick, plectron
(hypernym) device
(hyponym) guitar pick

(n.)
A small instrument of ivory, wood, metal, or quill, used in playing upon the lyre and other stringed instruments.
  

N
quill/ plectrum/pick (to strike strings of musical instrument); keyboard key