maddeningly

adjective

1. driving to madness or frenzy: a maddening thirst.
2. infuriating or exasperating: his maddening indifference to my pleas.
3. raging; furious: a maddening wind.

adjective

1. serving to send mad
2. extremely annoying; exasperating

adj.1743, from present participle of madden. Related: Maddeningly.