THIEVISHLY
thievishly
(adverb) in a manner characteristic of a thief
Source: WordNet® 3.1
Etymology
Adverb
thievishly (comparative more thievishly, superlative most thievishly)
In a thievish manner; like a thief.
Source: Wiktionary
THIEVISH
Thiev"ish, a.
1. Given to stealing; addicted to theft; as, a thievish boy, a
thievish magpie.
2. Like a thief; acting by stealth; sly; secret.
Time's thievish progress to eternity. Shak.
3. Partaking of the nature of theft; accomplished by stealing;
dishonest; as, a thievish practice.
Or with a base and biosterous sword enforce A thievish living on the
common road. Shak.
– Thiev"ish*ly, adv.
– Thiev"ish*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition