The Collaborative International Dictionary of English v.0.48:

Pickup \Pick"up\, or Pick-up \Pick"-up`\, n. [Colloq., Cant, or
   Slang]
   1. Act of picking up, as, in various games, the fielding or
      hitting of a ball just after it strikes the ground.
      [Webster 1913 Suppl.]

   2. That which picks up; specif.: (Elec.) same as Brush b.
      [Webster 1913 Suppl.]

   3. One that is picked up, as a meal hastily got up for the
      occasion, a chance acquaintance, an informal game, etc.
      [Webster 1913 Suppl.]

   4. a social companion for the evening who is met without
      prior arrangement, as at a singles bar; also, the act of
      joining with such a companion in that fashion.
      [PJC]

   5. (Automobiles) acceleration; a measure of the ability of a
      vehicle to accelerate.
      [PJC]

   6. (Electronics) a component of a phonograph which contains
      the stylus and also components for converting the
      vibrations of the stylus into electrical impulses for
      subsequent processing into sound; often referred to as a
      cartridge; also, the process of converting vibrations
      into electrical impulses.
      [PJC]

   7. (Electronics) the conversion of sound or light into
      electrical signals in a sound or image recording or
      transmitting device.
      [PJC]

   8. (Vehicles) a small truck having an enclosed driver's
      compartment (cab) but an open rear with usually low sides
      and a tailgate. Also called pickup truck.
      [PJC]

   9. a hitchhiker who has been picked up.
      [PJC]

WordNet (r) 3.0 (2006):

pickup
    n 1: a light truck with an open body and low sides and a
         tailboard [syn: pickup, pickup truck]
    2: a warrant to take someone into custody; "put out a pickup on
       that man"
    3: anything with restorative powers; "she needed the pickup that
       coffee always gave her" [syn: pickup, pick-me-up]
    4: a casual acquaintance; often made in hope of sexual
       relationships
    5: the attribute of being capable of rapid acceleration; "his
       car has a lot of pickup" [syn: pickup, getaway]
    6: mechanical device consisting of a light balanced arm that
       carries the cartridge [syn: tone arm, pickup, pickup
       arm]
    7: an electro-acoustic transducer that is the part of the arm of
       a record player that holds the needle and that is removable
       [syn: cartridge, pickup]
    8: the act or process of picking up or collecting from various
       places; "garbage pickup is on Mondays and Thursdays"
    9: the act of taking aboard passengers or freight