IPA: //ˈsɛmɪˌkweɪvə//
KK: /ˈsɛmɪˌkweɪvər/
A musical note that lasts for half the duration of an eighth note, commonly used in music notation.
In the piece, the composer used several semiquavers to create a fast rhythm.
Semiquaver → It is formed from "semi-" (meaning half) and "quaver" (from Old English *cwæfre*, meaning to shake or tremble). The word "semiquaver" refers to a musical note that is half the length of a quaver, thus indicating a note that is half in duration.
Think of 'half' ('semi-') of a note that 'shakes' or 'trembles' ('quaver') — that's why a semiquaver is a very short musical note.