persistent

persisting, especially in spite of opposition, obstacles, discouragement, etc.; persevering.

a most annoyingly persistent young man.

Synonyms:

tenacious, pertinacious, indefatigable

lasting or enduring tenaciously.

the persistent aroma of verbena; a persistent cough.

constantly repeated; continued.

persistent noise.

Synonyms:

steady, constant

Antonyms:

sporadic

Biology.

1. continuing or permanent.

2. having continuity of phylogenetic characteristics.

Botany. remaining attached beyond the usual time, as flowers, flower parts, or leaves.

showing persistence

incessantly repeated; unrelenting

your persistent questioning

(of plant parts) remaining attached to the plant after the normal time of withering

a fruit surrounded by a persistent perianth

zoology

1. (of parts normally present only in young stages) present in the adult

   persistent gills in axolotls

2. continuing to grow or develop after the normal period of growth

   persistent teeth

(of a chemical, esp when used as an insecticide) slow to break down; not easily degradable