Ludicrous (adjective)

1. Laughable because of being foolish or unreasonable.
2. Absurd, ridiculous.

Origin:

Mid 16th century: from latin ludicrous "laughable", from ludicrus "sportive" (from ludus "game").

Examples:

1. The idea that aliens are living among us is ludicrous.
2. The story he told us was so far-fetched that it was almost ludicrous.
3. The price of the product is absolutely ludicrous.
4. The notion that the earth is flat is a ludicrous one.
5. The proposal was so ridiculous that it was considered a ludicrous idea.