Though this word is not found in most English translations of the New Testament, the thought is there in the Greek text. It is an anglicized form of the original term antitupos. The term is rendered "like-figure" (1 Pet. 3:21) and "figure" (Heb. 9:24).
Literally, a tupos was a mark, or impression, produced by a blow (cf. Jn. 20:25). Therefore, the antitype stands over against, or corresponds to, the type.
The Old Testament contains many "types" or "shadows" that find their reality (fulfillment) in Christ. The Passover lamb was a type of Christ (Jn. 1:29; 1 Cor. 5:7). Moses was a type of Christ (Dt. 18:15ff; Acts 3:22).
In 1 Peter 3:21, the apostle argues that Noah's salvation from a wicked world through water pictured our deliverance from the guilt of sin through immersion in water (i.e., when one, with penitent faith, submits to baptism). Noah's salvation was the type. Our salvation is the antitype. See TYPE.