adjective

1. refusing to relent; continuing, esp. in the face of opposition, interference, etc.; stubborn; persevering
2. continuing to exist or endure; lasting without change
3. constantly repeated; continued
4. Bot. remaining attached permanently or for a longer than normal time, as some leaves, perianths, etc.
5. Zool.
   1. remaining essentially unchanged over a long period of geologic time, as a species
   2. remaining for life: said of such parts retained in the adult that normally disappear or wither at an early stage

Etymology: L persistens, prp. of persistere: see persist