VERB (5)

1. divide society into social classes or castes;
- Example: "Income distribution often stratifies a society"

2. form layers or strata;
- Example: "The rock stratifies"

3. develop different social levels, classes, or castes;
- Example: "Society stratifies when the income gap widens"

4. form, arrange, or deposit in layers;
- Example: "The fish are stratified in barrels"
- Example: "The rock was stratified by the force of the water"
- Example: "A statistician stratifies the list of names according to the addresses"

5. render fertile and preserve by placing between layers of earth or sand;
- Example: "stratify seeds"

The Collaborative International Dictionary of English v.0.48:

Stratify \Strat"i*fy\, v. t. [imp. & p. p. Stratified; p. pr.
   & vb. n. Stratifying.] [Stratum + -fy: cf. F. stratifier.]
   To form or deposit in strata, or layers, as substances in the
   earth; to arrange in strata.
   [1913 Webster] Stratigraphic

WordNet (r) 3.0 (2006):

stratify
    v 1: divide society into social classes or castes; "Income
         distribution often stratifies a society"
    2: form layers or strata; "The rock stratifies"
    3: develop different social levels, classes, or castes; "Society
       stratifies when the income gap widens"
    4: form, arrange, or deposit in layers; "The fish are stratified
       in barrels"; "The rock was stratified by the force of the
       water"; "A statistician stratifies the list of names
       according to the addresses"
    5: render fertile and preserve by placing between layers of
       earth or sand; "stratify seeds"