From BiblePortal Wikipedia

Morrish Bible Dictionary [1]

The word antitype does not occur in the A.V., but the Greek word ἀντίτυπονoccurs in  Hebrews 9:24 , translated 'figures,' and in  1 Peter 3:21 , translated 'like figure.' It is that which answers to a type, as a wax impression answers to a seal: if the device is sunk, the impression will be raised, or vice versa. To take a simple but beautiful example, a lamb was offered up for a burnt offering both morning and evening under the law; and in the N.T. we read, "Behold the Lamb of God, which taketh away the sin of the world." It is plain that the morning and evening lamb in Israel were types and the death of the Lord Jesus was the antitype. In  Hebrews 9:23 , the 'heavenly things' are the type, and 'holy places,'  Hebrews 9:24 , the antitype, or what corresponded to the pattern. In  1 Peter 3:21 , eight souls were saved through water, of which baptism is the figure, or what answers to it. Doubtless there are many other antitypes in the N.T., but every antitype must have a type to which it corresponds, though the correspondence may not lie on its surface. Where scripture is silent as to types and antitypes the teaching of the Holy Spirit is needed, or grievous error may result in associating two things together which have no spiritual connection, though names and words may seem to correspond.

Charles Buck Theological Dictionary [2]

A Greek word, properly signifying a type or figure corresponding to some other type. The word antitype occurs twice in the New Testament, viz. in the Epistle to the Hebrews, chap. 9: 5: 24, and in the 1 Epistle of St. Peter chap. 3: 5: 21. where its genuine import has been much controverted. The former says, that Christ is not entered into the holy places made with hands, which are the figures or antitypes of the true

now to appear in the presence of God. Now the Greek signifies the pattern by which another thing is made; and as Moses was obliged to make the tabernacle, and all things in it, according to the pattern shown him in the Mount, the tabernacle so formed was the antitype of what was shown to Moses: any thing, therefore, formed according to a model or pattern, is an antitype. In the latter passage, the apostle, speaking of Noah's flood, and the deliverance only of eight persons in the ark from it, says, Baptism being an antitype to that, now saves us; not the putting away of the filth of the flesh, but the answer of a good conscience towards God, &c. The meaning is, that righteousness, or the answer of a good conscience towards God, now saves us, by means of the resurrection of Christ, as formerly righteousness saved these eight persons by means of the ark during the flood. The word antitype, therefore, here signifies a general similitude of circumstances; and the particle whereunto, refers not to the immediate antecedent water, but to all that precedes.

Watson's Biblical & Theological Dictionary [3]

that which answers to a type or figure. A type is a model, mould, or pattern; that which is formed according to it is an antitype. See Type .

Webster's Dictionary [4]

(n.) That of which the type is the pattern or representation; that which is represented by the type or symbol.

Hastings' Dictionary of the New Testament [5]

See type.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [6]

that which answers to a type or figure. The corresponding Greek word,

Ἀντίτυπος , occurs twice in the New Testament ( Hebrews 9:24;  1 Peter 3:21), where it is rendered "figure" (q.v.). A type, in its primary and literal meaning, simply denotes a rough draught, or less accurate model, from which a more perfect image is made; but in the sacred and theological sense of the term, a type may be defined to be a symbol of something future and distant, or an example prepared and evidently designed by God to prefigure that future thing. What is thus prefigured is called the antitype. (See Type).