A federal insurance program that provides free or low-cost health coverage to some low-income people, families and children, pregnant women, the elderly, and people with disabilities. Many states have expanded their Medicaid programs to cover all people below certain income levels as part of Obamacare. Medicaid benefits, and program names, vary somewhat between states.
You can apply for Medicaid at anytime (there is no designated open enrollment period). If you qualify, your coverage can begin immediately, any time of year.