persistent
1. [ adjective ] never-ceasing
Synonyms: relentless unrelenting
Examples:

"the relentless beat of the drums"

Related terms: continual
2. [ adjective ] continually recurring to the mind
Synonyms: haunting
Examples:

"haunting memories" "the cathedral organ and the distant voices have a haunting beauty"- Claudia Cassidy

Related terms: unforgettable
3. [ adjective ] (biology) retained; not shed
Synonyms: lasting
Examples:

"persistent leaves remain attached past maturity" "the persistent gills of fishes"

Related terms: caducous biology
Similar spelling:   persistently
  persist
  persistency
  persistence
  persisting
  persist_in
  persecute
  persecutor
  persecuted
  Perseus
  Persichetti
  persecution
  Persechino