If you Google search

cougar woman

you will find lots of WWW sites defining the ages.

One site says this term refers to "women who pursue sexual relationships with men who are over eight years younger than them."

Another one says, "Although there are no precise ages, the woman is usually 35 years or older with the man more than eight years her junior."

Yet another says, "'Cougars' are popularly defined as women in their 40s (or older) who date significantly younger men, generally at a 10-year age gap or more ... The generally accepted age group for cougars is 40-plus; however, some people go as low as 35 in their definition."