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ambush - To suddenly attack someone after hiding and waiting for them:
The brigade walked quietly to the hidden spot on the hill, patiently until the enemy walked in the valley below, so that they could ambush the unsuspecting enemy, who were taken by surprise.
absurd - (of an idea or suggestion) wildly unreasonable, illogical, or inappropriate

When Edwin Hubble in 1929 suggested that some of the little dots of light in the sky were other galaxies, many people though the idea was absurd, but he was proven to be correct.