ul·tra 
(ŭltrə)
(ŭltrə)adj.
Immoderately adhering to a belief, fashion, or course of action; extreme.
n.
An extremist.
[French, from Latin ultrā-, ultra-.]
- petrochemical
- petrochemistry
- petrodollars
- petrogenesis
- petrogenetic
- petroglyph
- petroglyphic
- Petrograd
- petrographer
- petrographic
- petrographical
- petrographically
- petrography
- petrol
- petrolatum
- petroleum
- petroleum coke
- petroleum ether
- petroleum jelly
- petrolic
- petrologic
- petrological
- petrologically
- petrologist
- petrology