What is the definition of primary coverage in regard to medical insurance?

Often, a person will have "primary" insurance and "secondary" insurance. For example, if you have insurance through your job, and your husband has insurance through his job, then your primary insurance will be the one through your job, and your secondary insurance will be the one through your husband's job. Also, your husband's insurance through his job will be his primary, and yours through your job will be his secondary. There can be some exceptions to this though. For example, if you were married, had a child, then divorced and remarried (retaining custody of the child), and both your ex and current husbands have insurance through work, then the one who's birthday is first is considered the "primary" insurance, and the other is the "secondary" insurance. But there will still be a deductible with each one that has to be met before either one will pay.