The definition of a "Definite work of grace" is an experience or work that you must go through in order to become a mature Christian.

To the first century Christians the work of grace (as it is called) is Regeneration by which God revels himself to the sinner and through a new birth the sinner becomes a believer. They used the Greek word amartiV for sin, meaning "to miss the mark." They recognized that Christians can’t practice sin (1 John 3:9) but in times of emotional stress the sin nature pops out (Romans 7:14-8:2). We are to be conformed to the image of Jesus (Romans 8:29). As Paul said Romans 6:19 ...Just as you used to offer the parts of your body in slavery to impurity and to ever-increasing wickedness, so now offer them in slavery to righteousness leading to holiness. This is called progressive sanctification or in other words progressively setting yourself apart for God.
The words for sanctification and holiness refer to being set apart ready to do the work of God. They have little to do with righteousness or sin.

In the 1800’s the "Holiness movement" began teaching there was a second definite work of grace in addition to progressive sanctification. This was entire sanctification.
1 Thessalonians 5:23 May the God of peace himself sanctify you entirely; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ.

The first century church taught this scripture meant having an attitude willing to do whatever God called you to do to the beast of your ability. Not at all meaning how little you sinned, but how much you did for the LORD. Now; however, sin was redefined as only "willfully breaking a known law." Since a Christian will yield to the Holy Spirit and of course never willfully practice sin (1 John 3:9) by this definition he is totally sinless.

In the 1900’s the "Pentecostal movement" started teaching there was a second definite work of grace called the infilling of the Spirit. The sign of which is speaking in tongues.
In speaking of the gift of tongues Paul says in 1 Corinthians 12:11 "All these are the work of one and the same Spirit, and he gives them to each one, just as he determines." and in verse 29 "Do all speak in tongues? Do all interpret?" The answer of course is no.
The Holy Spirit gives what gifts he wants, when he wants, for however long he wants. The Holy Spirit will not let everyone speak in tongues or interpret. Most Christians have none of these gifts and that is by his design.

In the mid 1900’s some of these two groups mixed. They stated that Entire sanctification was a second definite work of grace and that the infilling (tongues) was the third definite work of grace. However some thought tongues was the second and sanctification was the third.

A fourth definite work of grace would be doctrinal perfection.
Scriptures like: "the Holy Spirit... will teach you all things" (John 14:26), "we have the mind of Christ" (1 Corinthians 2:16), "I thought as a child...but when I became a man I put away childish things" (1 Corinthians 13:11) and "having all power, knowledge, tongues, faith and prophecy" (1 Corinthians 13:1-4) are used to support doctrinal perfection. However; these scriptures are taken out of context.

Saying that entire sanctification, tongues or doctrinal perfection is a definite work, or in other words something you must have in order to be a mature Christian, is an error.
We see the apostle Paul still struggled with the sin nature (Romans 7) and toward the end of his life he stated he still had not reached the mark (Philippians 3:12) but since he walked in faith it was not counted against him (Romans 8:1). If we claim to be sinless we are liars (1 John 1:8). Not everyone is supposed to speak in tongues (1 Corinthians 12:11,29). Now we don’t understand everything perfectly but we will in the resurrection (1 Corinthians 13:12).

All quotations taken from the NIV unless other wise noted. Rev. 1