A Pound of Thoughts

fractious \FRAK-shuhs\, adjective:
1. Tending to cause trouble; unruly.
2. Irritable; snappish; cranky.

Example Sentence: 

Marcus frequently took a rod to Ambrose’s back–with the predictable result of making the boy even more fractious and slow to obey.
– Roy Morris Jr., Ambrose Bierce: Alone in Bad Company

Origin:  Fractious is from fraction, which formerly had the sense “discord, dissension, disharmony”; it is derived from Latin frangere, “to break.”

Note:  Not to be confused with a previous word of the day, factious.
Source:  Dictionary.com