mustard seed

/M AH1 S T ER0 D S IY1 D/
noun
  1. 1

    A small, round seed of the mustard plant.

  2. 2

    (figuratively) A small amount.

  3. 3

    (firearms, also attributively) Small lead shot, usually of size No. 12, used for shooting birds and other animals at close range.