A database like Genbank is said to be a nonreductive database. What does that mean ?
If your instructor told you that I think they are wrong.
This link http://blast.ncbi.nlm.nih.gov/Blast.cgi?CMD=Web&PAGE_TYPE=BlastDocs&DOC_TYPE=ProgSelectionGuide at Table 2.1 has:
nr Non-redundant GenBank CDS translations + PDB + SwissProt + PIR + PRF, excluding those in env_nr.
suggesting that nr meand Non-redundant, not nonreductive.