The Collaborative International Dictionary of English v.0.48:

Senecas \Sen"e*cas\, n. pl.; sing. Seneca. (Ethnol.)
   A tribe of Indians who formerly inhabited a part of Western
   New York. This tribe was the most numerous and most warlike
   of the Five Nations.
   [1913 Webster]

   Seneca grass(Bot.), holy grass. See under Holy.

   Seneca eil, petroleum or naphtha.

   Seneca root, or Seneca snakeroot (Bot.), the rootstock of
      an American species of milkworth (Polygala Senega)
      having an aromatic but bitter taste. It is often used
      medicinally as an expectorant and diuretic, and, in large
      doses, as an emetic and cathartic. [Written also Senega
      root, and Seneka root.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

Seneca
    n 1: Roman statesman and philosopher who was an advisor to Nero;
         his nine extant tragedies are modeled on Greek tragedies
         (circa 4 BC - 65 AD) [syn: Seneca, Lucius Annaeus
         Seneca]
    2: a member of the Iroquoian people formerly living in New York
       State south of Lake Ontario
    3: the Iroquoian language spoken by the Seneca

The Free On-line Dictionary of Computing (30 December 2018):

Oberon-V
Seneca

   (Formerly Seneca).  R. Griesemer, 1990.  Descendant of Oberon
   designed for numerical applications on supercomputers,
   especially vector or pipelined architectures.  Includes array
   constructors and an ALL statement.  "Seneca - A Language for
   Numerical Applications on Vectorcomputers", Proc CONPAR 90 -
   VAPP IV Conf.  R. Griesemer, Diss Nr. 10277, ETH Zurich.


U.S. Gazetteer Counties (2000):

Seneca -- U.S. County in Ohio
   Population (2000):    58683
   Housing Units (2000): 23692
   Land area (2000):     550.587565 sq. miles (1426.015186 sq. km)
   Water area (2000):    1.781014 sq. miles (4.612806 sq. km)
   Total area (2000):    552.368579 sq. miles (1430.627992 sq. km)
   Located within:       Ohio (OH), FIPS 39
   Location:             41.128917 N, 83.173728 W
   Headwords:
    Seneca
    Seneca, OH
    Seneca County
    Seneca County, OH


U.S. Gazetteer Counties (2000):

Seneca -- U.S. County in New York
   Population (2000):    33342
   Housing Units (2000): 14794
   Land area (2000):     324.912952 sq. miles (841.520646 sq. km)
   Water area (2000):    65.600825 sq. miles (169.905350 sq. km)
   Total area (2000):    390.513777 sq. miles (1011.425996 sq. km)
   Located within:       New York (NY), FIPS 36
   Location:             42.801104 N, 76.827879 W
   Headwords:
    Seneca
    Seneca, NY
    Seneca County
    Seneca County, NY


U.S. Gazetteer Places (2000):

Seneca, MO -- U.S. city in Missouri
   Population (2000):    2135
   Housing Units (2000): 876
   Land area (2000):     1.734021 sq. miles (4.491094 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.734021 sq. miles (4.491094 sq. km)
   FIPS code:            66674
   Located within:       Missouri (MO), FIPS 29
   Location:             36.840318 N, 94.609918 W
   ZIP Codes (1990):     64865
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, MO
    Seneca


U.S. Gazetteer Places (2000):

Seneca, NE -- U.S. village in Nebraska
   Population (2000):    51
   Housing Units (2000): 52
   Land area (2000):     0.120623 sq. miles (0.312411 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.120623 sq. miles (0.312411 sq. km)
   FIPS code:            44385
   Located within:       Nebraska (NE), FIPS 31
   Location:             42.042717 N, 100.831763 W
   ZIP Codes (1990):     69161
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, NE
    Seneca


U.S. Gazetteer Places (2000):

Seneca, OR -- U.S. city in Oregon
   Population (2000):    223
   Housing Units (2000): 115
   Land area (2000):     0.832671 sq. miles (2.156607 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.832671 sq. miles (2.156607 sq. km)
   FIPS code:            66200
   Located within:       Oregon (OR), FIPS 41
   Location:             44.135605 N, 118.971854 W
   ZIP Codes (1990):     97873
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, OR
    Seneca


U.S. Gazetteer Places (2000):

Seneca, IL -- U.S. village in Illinois
   Population (2000):    2053
   Housing Units (2000): 786
   Land area (2000):     3.307397 sq. miles (8.566118 sq. km)
   Water area (2000):    0.258224 sq. miles (0.668796 sq. km)
   Total area (2000):    3.565621 sq. miles (9.234914 sq. km)
   FIPS code:            68640
   Located within:       Illinois (IL), FIPS 17
   Location:             41.308618 N, 88.607010 W
   ZIP Codes (1990):     61360
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, IL
    Seneca


U.S. Gazetteer Places (2000):

Seneca, PA -- U.S. Census Designated Place in Pennsylvania
   Population (2000):    966
   Housing Units (2000): 432
   Land area (2000):     2.242412 sq. miles (5.807819 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.242412 sq. miles (5.807819 sq. km)
   FIPS code:            69272
   Located within:       Pennsylvania (PA), FIPS 42
   Location:             41.377828 N, 79.703224 W
   ZIP Codes (1990):     16346
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, PA
    Seneca


U.S. Gazetteer Places (2000):

Seneca, KS -- U.S. city in Kansas
   Population (2000):    2122
   Housing Units (2000): 978
   Land area (2000):     1.543272 sq. miles (3.997055 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.543272 sq. miles (3.997055 sq. km)
   FIPS code:            63950
   Located within:       Kansas (KS), FIPS 20
   Location:             39.835693 N, 96.066054 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, KS
    Seneca


U.S. Gazetteer Places (2000):

Seneca, SC -- U.S. city in South Carolina
   Population (2000):    7652
   Housing Units (2000): 3677
   Land area (2000):     7.055264 sq. miles (18.273048 sq. km)
   Water area (2000):    0.038215 sq. miles (0.098976 sq. km)
   Total area (2000):    7.093479 sq. miles (18.372024 sq. km)
   FIPS code:            65095
   Located within:       South Carolina (SC), FIPS 45
   Location:             34.684145 N, 82.955778 W
   ZIP Codes (1990):     29678
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, SC
    Seneca


U.S. Gazetteer Places (2000):

Seneca, SD -- U.S. town in South Dakota
   Population (2000):    58
   Housing Units (2000): 36
   Land area (2000):     0.411362 sq. miles (1.065423 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.411362 sq. miles (1.065423 sq. km)
   FIPS code:            58180
   Located within:       South Dakota (SD), FIPS 46
   Location:             45.060962 N, 99.509911 W
   ZIP Codes (1990):     57473
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Seneca, SD
    Seneca