An obsolete Vulcan ritual that represses a memory together with the emotions attached to it, performed on T'Pol at P'Jem after she killed a fugitive on Risa.
The fullara is a Vulcan mental procedure that buries a specific memory and the feelings bound up with it. By the 22nd century it was regarded as outdated, but it was still carried out by the monks of P'Jem.
It is revealed in the Enterprise episode The Seventh. Years before joining Enterprise, T'Pol was sent by the Vulcan Ministry of Security to bring back agents who had refused to return from an undercover assignment. On Risa she shot one of them, Jossen, and was so shaken that she resigned and underwent the fullara.
When she is ordered to capture Menos, the last of the fugitives, the suppressed memory begins to surface. With Jonathan Archer's support she recovers what happened and completes the mission.