The Collaborative International Dictionary of English v.0.48:
Monthly \Month"ly\, a. 1. Continued a month, or a performed in a month; as, the monthly revolution of the moon. [1913 Webster] 2. Done, happening, payable, published, etc., once a month, or every month; as, a monthly visit; monthly charges; a monthly installment; a monthly magazine. [1913 Webster] Monthly nurse, a nurse who serves for a month or some short time, esp. one which attends women after childbirth. [1913 Webster]