From The Collaborative International Dictionary of English v.0.48 [gcide]:
Aggregative \Ag"gre*ga*tive\, a. [Cf. Fr. agr['e]gatif.]
1. Taken together; collective.
[1913 Webster]
2. Gregarious; social. [R.] --Carlyle.
[1913 Webster]
3. tending to gather into a mass.
[WordNet 1.5]
From WordNet (r) 3.0 (2006) [wn]:
aggregative
adj 1: formed of separate units gathered into a mass or whole;
"aggregate expenses include expenses of all divisions
combined for the entire year"; "the aggregated amount of
indebtedness" [syn: aggregate, aggregated,
aggregative, mass]