persistent

(s) never-ceasing
- the relentless beat of the drums
relentless, unrelenting,
(s) continually recurring to the mind
- haunting memories
- "the cathedral organ and the distant voices have a haunting beauty"- Claudia Cassidy
haunting,
(a) retained; not shed
- persistent leaves remain attached past maturity
- the persistent gills of fishes
lasting,
(s) stubbornly unyielding
- dogged persistence
- dour determination
- the most vocal and pertinacious of all the critics
- "a mind not gifted to discover truth but tenacious to hold it"- T.S.Eliot
- men tenacious of opinion
dogged, dour, pertinacious, unyielding, tenacious,

relentless unrelenting haunting lasting dogged dour pertinacious unyielding tenacious

caducous shed

persistently