Synonyms of slyly

2 Syllables
shrewdly
3 Syllables
stealthily, privily, artfully, secretly, untruly, cunningly, trickily, craftily, foxily, shiftily, covertly
4 Syllables
insidiously, furtively, untruthfully, deceivingly, mendaciously, guilefully
5 Syllables
intelligently, deceptively, underhandedly