According to the Australian Taxation Office (ATO) a reversionary pension is a pension which reverts to a beneficiary (usually a spouse) on the death of the member.
A reversionary pension is simply a pre-existing income stream/pension payable to a dependant (reversionary beneficiary) on the death of the primary pension fund member. Note that a reversionary pension is not a new pension but simply a redirection of the pre-existing pension to the reversionary pensioner. Reversionary pensions are typically paid to the surviving spouse.
The reversionary beneficiary is the person nominated by a member of the superannuation fund to automatically receive an income stream (pension / annuity) upon the member's death.