An alternative plan or offer is different from the one that you already have, and can be done or used instead.

Alternative is used to describe something that is different from the usual things of its kind, or the usual ways of doing something, in modern Western society. For example, an alternative lifestyle does not follow conventional ways of living and working.

Alternative medicine uses traditional ways of curing people, such as medicines made from plants, massage, and acupuncture.

Alternative energy uses natural sources of energy such as the sun, wind, or water for power and fuel, rather than oil, coal, or nuclear power.

If one thing is an alternative to another, the first can be found, used, or done instead of the second.