'September' definitions:

Definition of 'September'

(from WordNet)
noun
The month following August and preceding October [syn: September, Sep, Sept]

Definition of 'September'

From: GCIDE
  • September \Sep*tem"ber\, n. [L., fr. septem seven, as being the seventh month of the Roman year, which began with March: cf. F. septembre. See Seven.] The ninth month of the year, containing thurty days. [1913 Webster]