DISASTROUSLY
disastrously
(adverb) in a disastrous manner; “the real value of the trust capital may be disastrously less than when the trust began”
Source: WordNet® 3.1
Etymology
Adverb
disastrously (comparative more disastrously, superlative most disastrously)
In a disastrous way. (Of the nature of a disaster; calamitously.)
Source: Wiktionary
DISASTROUS
Dis*as"trous, a. Etym: [Cf. F. désastreux. See Disaster.]
1. Full of unpropitious stellar influences; unpropitious; ill-boding.
[Obs.]
The moon In dim eclipse, disastrous twilight sheds. Milton.
2. Attended with suffering or disaster; very unfortunate; calamitous;
ill-fated; as, a disastrous day; a disastrous termination of an
undertaking.
Wherein I spake of most disastrous chances. Shak.
– Dis*as"trous*ly, adv.
– Dis*as"trous*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition