The Collaborative International Dictionary of English v.0.48:

Seven \Sev"en\, a. [OE. seven, seoven, seofen, AS. seofon,
   seofan, seofen; akin to D. zeven, OS., Goth., & OHG. sibun,
   G. sieben, Icel. sjau, sj["o], Sw. sju, Dan. syv, Lith.
   septyni, Russ. seme, W. saith, Gael. seachd, Ir. seacht, L.
   septem, Gr. ???, Skr. saptan. [root]305. Cf. Hebdomad,
   Heptagon, September.]
   One more than six; six and one added; as, seven days make one
   week.
   [1913 Webster]

   Seven sciences. See the Note under Science, n., 4.

   Seven stars (Astron.), the Pleiades.

   Seven wonders of the world. See under Wonders.

   Seven-year apple (Bot.), a rubiaceous shrub (Genipa
      clusiifolia) growing in the West Indies; also, its edible
      fruit.

   Seven-year vine (Bot.), a tropical climbing plant
      (Ipom[oe]a tuberosa) related to the morning-glory.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Seven \Sev"en\, n.
   1. The number greater by one than six; seven units or
      objects.
      [1913 Webster]

            Of every beast, and bird, and insect small,
            Game sevens and pairs.                --Milton.
      [1913 Webster]

   2. A symbol representing seven units, as 7, or vii.
      [1913 Webster]

WordNet (r) 3.0 (2006):

seven
    adj 1: being one more than six [syn: seven, 7, vii]
    n 1: the cardinal number that is the sum of six and one [syn:
         seven, 7, VII, sevener, heptad, septet,
         septenary]
    2: one of four playing cards in a deck with seven pips on the
       face [syn: seven-spot, seven]

Easton's 1897 Bible Dictionary:

Seven
   This number occurs frequently in Scripture, and in such
   connections as lead to the supposition that it has some typical
   meaning. On the seventh day God rested, and hallowed it (Gen.
   2:2, 3). The division of time into weeks of seven days each
   accounts for many instances of the occurrence of this number.
   This number has been called the symbol of perfection, and also
   the symbol of rest. "Jacob's seven years' service to Laban;
   Pharaoh's seven fat oxen and seven lean ones; the seven branches
   of the golden candlestick; the seven trumpets and the seven
   priests who sounded them; the seven days' siege of Jericho; the
   seven churches, seven spirits, seven stars, seven seals, seven
   vials, and many others, sufficiently prove the importance of
   this sacred number" (see Lev. 25:4; 1 Sam. 2:5; Ps. 12:6; 79:12;
   Prov. 26:16; Isa. 4:1; Matt. 18:21, 22; Luke 17:4). The feast of
   Passover (Ex. 12:15, 16), the feast of Weeks (Deut. 16:9), of
   Tabernacles (13:15), and the Jubilee (Lev. 25:8), were all
   ordered by seven. Seven is the number of sacrifice (2 Chr.
   29:21; Job 42:8), of purification and consecration (Lev. 42:6,
   17; 8:11, 33; 14:9, 51), of forgiveness (Matt. 18:21, 22; Luke
   17:4), of reward (Deut. 28:7; 1 Sam. 2:5), and of punishment
   (Lev. 26:21, 24, 28; Deut. 28:25). It is used for any round
   number in such passages as Job 5:19; Prov. 26:16, 25; Isa. 4:1;
   Matt. 12:45. It is used also to mean "abundantly" (Gen. 4:15,
   24; Lev. 26:24; Ps. 79:12).