Wordnet 3.0
NOUN (1)
1. 
 from 2,500 to 544 million years ago; 
 bacteria and fungi; 
 primitive multicellular organisms; 
[syn: Proterozoic, Proterozoic eon, Proterozoic aeon]
ADJECTIVE (1)
1.  formed in the later of two divisions of the Precambrian era; 
- Example: "proterozoic life forms"
WordNet (r) 3.0 (2006):
proterozoic
    adj 1: formed in the later of two divisions of the Precambrian
           era; "proterozoic life forms"
    n 1: from 2,500 to 544 million years ago; bacteria and fungi;
         primitive multicellular organisms [syn: Proterozoic,
         Proterozoic eon, Proterozoic aeon]