insidiously
in-sid-i-ous-ly
adverb
In a gradual, subtle, and often harmful or destructive manner.
"The problem developed insidiously over many years."
Thesaurus
Synonyms: perniciously
in-sid-i-ous-ly
In a gradual, subtle, and often harmful or destructive manner.
"The problem developed insidiously over many years."
Synonyms: perniciously