A genuine truthful idea, concept, fact or truth that is unsettling, uncomfortable for the larger mainstream society; where presentation of it, while truthful and liberating, may potentially bring about negative effect to their well-being.
In short, a flactrum is a dangerous uncomfortable truth.
A flactrum lives up to the high bar of truth, often with robust empirical basis. While highly disputed, holder of a flactrum truth is entirely honest and convinced about the untampered fact, and has adequate basis to back it up.
At the same time, a flactrum challenges the recipient to re-examine his reality, but fully expect him to reject this new idea for implying that the recipient's way of life has been faulty.
If a flactrum is not outright rejected in exchange for a blissful ignorance, the flactrum's conformity with the ideals of the recipient will be called into question.
In the best case, recipient may positively take advantage of this new reality and navigate it accordingly. In the worst case, his new awareness may create a state of void so profound it demotivate him to a point of no return.