persistent
adjective
never-ceasing
“the relentless beat of the drums”
continually recurring to the mind
“haunting memories”
“the cathedral organ and the distant voices have a haunting beauty”
Synonymshauntingretained; not shed
“persistent leaves remain attached past maturity”
“the persistent gills of fishes”
SynonymslastingOppositescaducousstubbornly unyielding
“dogged persistence”
“dour determination”
Source: WordNet 3.1, Princeton University
