IPA: /nɒnˈpleɪɪŋ/
KK: /nɑnˈpleɪɪŋ/
Not participating in a game or activity; not involved in play.
The nonplaying members of the team supported their friends from the sidelines.
Nonplaying → It is formed from "non-" (meaning not) and "playing" (from the verb "play", which has roots in Old English "plegian", meaning to engage in activity for enjoyment). The word "nonplaying" means not engaging in play or activity.
Think of 'not' ('non-') engaging in 'play' — that's why nonplaying means not participating in play.