1. Showing sustained enthusiastic action with unflagging vitality
   "unflagging pursuit of excellence"
   - indefatigable, tireless, unwearying 
2. Unceasing
   "unflagging courtesy"
   - unfailing

See also: constant, energetic

• genus Arceuthobium
• genus Archaeopteryx
• genus Archaeornis
• genus Archeopteryx
• genus Archidiskidon
• genus Archilochus
• genus Architeuthis
• genus Archosargus
• genus Arctictis
• genus Arctium
• genus Arctocebus
• genus Arctocephalus
• genus Arctonyx
• genus Arctostaphylos
• genus Arctotis
• genus Ardea
• genus Ardisia
• genus Areca
• genus Arenaria
• genus Arenga
• genus Arethusa
• genus Argemone
• genus Argentina
• genus Argentinosaurus
• genus Argiope