From The Dhamma Encyclopedia
Sammā-sambodhi also; Samma-sam-buddha: 'Perfect Enlightenment', Universal Buddhahood, is the state attained by a Universal Buddha sammā-sambuddha i.e. one by whom the liberating law Dhamma which had become lost to the world, has again been discovered, realized and clearly proclaimed to the world.
Now, someone, in things never heard before, understands by himself the truth, and he therein attains omniscience, and gains mastery in the powers. Such a one is called a Universal Buddha, or Enlightened One; Pug. 29.
The doctrine characteristie of all the Buddhas, and each time rediscovered by them and fully explained to the world, consists in the 4 Truths sacca of suffering, its origin, its ceasing and the way to its ceasing; The Four Noble Truths.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.