Ok, so at the end of the first page of the article I linked, it says "A dynamical system defined by a given Hamiltonian H on a 2 n-dimensional phase space 1 Ω is now called (completely) integrable if there exist additional functions H 1 , . . . , H n on Ω (again referred to as ‘Hamiltonians’) such that
H 1 , . . . , H n are independent and in involution (i.e., all Poisson brackets { H j , H k }
vanish). Thus these Hamiltonians are conserved under the Hamiltonian evolution on Ω generated by each of them"