Meaning of PRO- in English

PRO-

I. prefix

Etymology: New Latin, from Latin, from Greek, before, forward, forth, for, from pro — more at for

1.

a. : earlier than : prior to : before

pro thalamion

b. : rudimentary : prot-

pro nucleus

c. : precursory

pro insulin

2.

a. : located in front of or at the front of : anterior to

pro cephalic

pro ventriculus

b. : front : anterior

pro thorax

3. : projecting

pro gnathous

II. prefix

Etymology: Latin pro in front of, before, for, forward — more at for

1. : taking the place of : substituting for

pro cathedral

pro caine

2. : favoring : supporting : championing

pro- American

Merriam-Webster's Collegiate English vocabulary.      Энциклопедический словарь английского языка Merriam Webster.