The mentor definition, according to the dictionary, is a trusted advisor or guide. To me, a mentor is someone who is helping you with your career, specific work projects or general life advice out of the goodness of his or her heart. My definition of mentor includes altruism and some sense of "paying it forward" since most mentors have themselves been mentored in the past.
For working moms especially, it's crucial to have at least one mentor, but probably several, whom you can turn to for advice about a proposal to your boss or how to navigate a tricky client situation. Your mentor may also be the person who clues you in when it's time to leave an employer, or to ask for a raise.
If you find yourself being cultivated as a mentor, whether by a recent college graduate or someone more seasoned, think about what helped you along the way and try to provide that kind of support to your mentee. While it's tempting to think that you're wasting time by mentoring another individual, you actually are building your own network. You never know when you might lose your job and need help from people at all levels of your field. Moreover, social psychology research shows that people who help others at work are more likely to be promoted and earn more.