Source : Webster's Revised Unabridged Dictionary (1913)

Matriarch \Ma"tri*arch\, n. [L. mater mother + -arch.]
   The mother and ruler of a family or of her descendants; a
   ruler by maternal right.

Source : WordNet®

matriarch
     n 1: a female head of a family or tribe [syn: {materfamilias}]
     2: a feisty older woman with a big bosom (as drawn in cartoons)