challenging

Etymology

From Middle English chalengynge; equivalent to challenge + -ing.

verb

1. present participle and gerund of challenge

adj

1. Difficult, hard to do.

noun

1. The act of making a challenge.
   There are always sincere challengings of the findings, always the objections (sincere in another sense) of those whose interests seem threatened. 1918, Estcourt Rowland Metzner, The conflict of tax laws, page 151