I have two thoughts.

First, the 'cyclic' aspect might mean that your mom's depression cycles between a 'normal' (baseline) state and a depressed state.

Second, mania doesn't always look like happy, elated, euphoric, delusions of grandeur, spending a lot of money, and so on. There is an awful type of mania, or hypo-mania, called 'dysphoric mania'. With that type, a person feels very anxious, stressed, and can sometimes be irritable, quick to anger...and sometimes various moods occur at the same time. For example, a person with a rapid-cycling mood disorder can feel depressed, anxious, and euphoric very intensely and almost at the same time.

But the bottom line is that 'cyclic mood disorder' means the person experiences extreme moods in cycles...periods of time, on a regular basis.