UNIQUE WORDS game to increase our vocabulary - alphabetical order

Tontine - 

an annuity shared by subscribers to a loan or common fund, the shares increasing as subscribers die until the last survivor enjoys the whole income

• a scheme for life insurance in which the beneficiaries are those who survive and maintain a policy to the end of a given period

XO - Executive Officer (military), second in command

Abject - Wretched, completely without pride, miserable

dearth
an insufficient quantity or number

Fenestron - is a protected tail rotor of a helicopter operating like a ducted fan