What is Baptism By Fire?

Legal Definition
The phrase baptism by fire or baptism of fire is a phrase originating from the words of John the Baptist in Matthew 3:11.

Matthew 3:11 "I indeed baptize you with water unto repentance: but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize you with the Holy Ghost, and with fire" King James Version 1611

The phrase also occurs in Luke 3:16 and it might be taken as a reference to the fiery trial of faith which endures suffering and purifies the faithful who look upon God's glory and are transformed, not consumed (Mark 10:38, James 1:2-4, 1 Peter 1:7, 1 Peter 4:12). See also Dante's Purgatory 27:10-15.
-- Wikipedia
Legal Definition
An event that means success or failure for a company or party. This is common for new companies.