The synthesized Mn2FeAl alloys crystallize in a geometrically frustrated cubic beta-Mn structure (space group: P4(1)32) with an antiferromagnetic ordering whereas the previous theoretical findings suggest for a Heusler structure (L2(1): regular and X: inverse). The experimental stability of the structure is verified by electronic structure calculations performed for various arrangements of Mn, Fe and Al atoms in the beta-Mn-type crystal structure. When compared the energy of the beta-Mn structure with the energy of L2(1) and X type structures, it is found that for an expansion of the lattice volume beta-Mn structure becomes more preferable in total energy than L2(1) and X-type structures. The calculated theoretical equilibrium lattice parameter value for the beta-Mn-2 FeAl is within the accuracy of the experimental value obtained in this work. Additional DFT + U calculations for the optimized crystal structure of the beta-Mn2FeAl revealed that the electronic correlations in the Mn ions result in the increased total magnetic moment. In the X type structure, Mn2FeAl is a half metal, whereas the disordered arrangement of atoms in the beta-Mn structure leads to the closure of the semiconductor gap. The Mn2FeAl alloys exhibit antiferromagnetic ordering (T-N approximate to 42 K), which is in excellent agreement with our electronic structure calculations. The detailed analysis of the magnetic and heat capacity measurements suggests a short-range magnetic ordering in the Mn2FeAl alloys. Owing to the strong antiferromagnetic spin fluctuation caused by the geometric frustration in beta-Mn, a large enhancement in the electronic heat capacity is noticed. Mn2FeAl shows the characteristic features of spin glass as verified from the frequency dependent AC susceptibility analysis using critical power law and Vogel-Fulcher law. To the best of our knowledge, this is the first ever report on the theoretically predicted lowest ground state configuration for Mn2FeAl with a beta-Mn structure and the experimental realization of spin glass features in this geometrically frustrated antiferromagnet.