The description of the word you requested from the astronomical dictionary is given below.
The number of sunspots on the Sun varies fairly regularly with a period of about 11 years which is called the sunspot cycle. When the number of sunspots is smallest (zero or close to it) then the Sun is in the sunspot minimum. When the number of sunspots is greatest, then the Sun is in the sunspot maximum. The strength of other phenomenons changes with the number of sunspots, for example the number of solar flares and the number of coronal mass ejections. The sunspot cycle is therefore also called the solar activity cycle.