noun

• (Judaism) Food products made from leavened grain flour, which may not be consumed on Passover.
  "The eating of chametz (leavened products) is explicitly prohibited on Passover (Exod. 12:19–20; 13:3), for the Israelites “took their dough before it was leavened” (Exod. 12:34) and left Egypt in great haste."

adj

• (Judaism) Made of chametz.
  "It is permitted, therefore, to store and use all types of ointments, hand lotions, nail polish or medicated drops (for the ear or nose), etc., even if they contain an active chametz ingredient. […]"
• (Judaism) Used with or to be used with chametz.
  "One of the many preparations one must make for Pesach is kashering (a process to prepare a non-kosher vessel for kosher use or a chametz vessel for use on Pesach). […] All chametz utensils that will be used for Pesach must be thoroughly cleaned. […] Remove the filter covering the drain and put it away for Pesach with the chametz dishes. […] The pots may be chametz pots. […] Where needed, one can use a chametz microwave on Pesach by[…]"