Guaranteed issue in a life insurance policy means that you will not be turned down for coverage any reason, regardless of any health condition.  

Most life insurance policies go through full underwriting, which is where the life insurance company decides the degree of risk involved with insuring your life. For example, are you healthy and expected to live a long life or do you have health concerns that could potentially shorten your life expectancy?  

With a guaranteed issue life insurance policy, typically there is what they call a "graded death benefit" period in that the life insurance policy will not pay the full face amount death benefit for a period of time, typically 2 years but sometimes 3 years.