In a rhombus, the opposite angles are equal, and the adjacent angles are supplementary (they add up to 180 degrees).
Given that \( m \angle A = 114^\circ \) in rhombus ABCD, we can find \( m \angle B \) as follows:
Since \( m \angle A + m \angle B = 180^\circ \): \[ m \angle B = 180^\circ - m \angle A \] \[ m \angle B = 180^\circ - 114^\circ \] \[ m \angle B = 66^\circ \]
Thus, \( m \angle B = 66^\circ \).