A person easily duped or taken advantage of, as in You're a clay pigeon for all of those telephone fund-raisers. The term alludes to the clay pigeon of trapshooting, which replaced the use of live birds in this sport in the 1860s. Its transfer to figurative use in the first half of the 1900s probably is explained by the much older slang use of pigeon for "dupe." Also see fall guy.
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