  We study the implementation of the type III seesaw in the ordinary
nonsupersymmetric SU(5) grand unified theory. This allows for an alternative
definition of the minimal SU(5) model, with the inclusion of the adjoint
fermionic multiplet. The main prediction of the theory is the light fermionic
SU(2) triplet with mass at the electroweak scale. Due to their gauge couplings,
these triplets can be produced pair-wise via Drell-Yan, and due to the Majorana
nature of the neutral component their decays leave a clear signature of same
sign di-leptons and four jets. This allows for their possible discovery at LHC
and provides an example of directly measurable seesaw parameters.
