Definitions of bulk:

• noun:   the property possessed by a large mass
• noun:   the property of something that is great in magnitude

  Example: "It is cheaper to buy it in bulk"

• noun:   the property resulting from being or relating to the greater in number of two parts; the main part

  Example: "The bulk of the work is finished"

• verb:   stick out or up

  Example: "The parcel bulked in the sack"

• verb:   cause to bulge or swell outwards