noun used as a suffix, takes genitive case の

After the -masu stem of a verb.
  1. stopped in the midst of, half- (i.e. half-read).

Variations

Pronunciation Kanji Kana Is Common
 
止し さし

Contained Kanji Breakdown

stop, halt
と.まる シ どめ (2nd, N4)
divining, fortune-telling, divination or katakana to radical (no. 25)
ボク うらな.う うらない (Kentei Pre-1)