The Collaborative International Dictionary of English v.0.48:

Countryside \Coun"try*side`\ (-s?d`), n.
   A particular rural district; a country neighborhood. [Eng.]
   --W. Black. Blackmore.
   [1913 Webster]

WordNet (r) 3.0 (2006):

countryside
    n 1: rural regions

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "countryside":
   agricultural region, arable land, black belt, citrus belt,
   corn belt, cotton belt, dust bowl, farm belt, farm country,
   farmland, fruit belt, grass roots, grassland, grazing region,
   highlands, lowlands, meadows and pastures, moors, plains, prairies,
   province, provinces, rural district, rustic region, steppes,
   the country, the soil, the sticks, tobacco belt, uplands, veld,
   wheat belt, wide-open spaces, woodland, woods and fields,
   yokeldom



U.S. Gazetteer Places (2000):

Countryside, IL -- U.S. city in Illinois
   Population (2000):    5991
   Housing Units (2000): 2818
   Land area (2000):     2.690473 sq. miles (6.968292 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.690473 sq. miles (6.968292 sq. km)
   FIPS code:            16873
   Located within:       Illinois (IL), FIPS 17
   Location:             41.778885 N, 87.874006 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Countryside, IL
    Countryside


U.S. Gazetteer Places (2000):

Countryside, KS -- U.S. city in Kansas
   Population (2000):    295
   Housing Units (2000): 131
   Land area (2000):     0.120415 sq. miles (0.311874 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.120415 sq. miles (0.311874 sq. km)
   FIPS code:            15975
   Located within:       Kansas (KS), FIPS 20
   Location:             39.015985 N, 94.655297 W
   ZIP Codes (1990):     66202
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Countryside, KS
    Countryside