Explanation:

Irregular or Fasid Marriage:
Those marriages which are outcome of failures on part of parties in non fulfillment of prerequisites but then also are marriages; to be terminated by one of the party is termed to be Irregular marriages. They are outcome of-
(a) A marriage without witness (Not under Shia Law)
(b) Marriage with fifth wife.
(c) Marriage with a women undergoing Iddat.
(d) Marriage with a fire-worshipper.
(e) Marriage outcome of bar of unlawful conjunction.
An irregular marriage has no legal effect before consummation but when consummated give rise to several rights & obligations