A            In English, the shortest indefinite article

MA            Pa’s Mate

ATM            Cash dispensing device (abbr.)

ATOM            Its components are protons, neutrons and electrons

MOATS        Castle’s watery defense

ALMOST        Not quite, but very nearly

MORTALS        Unlike Greek Gods, mere humans who are subject to death

MORALIST        Aesop, for example

HAILSTORM        Weather phenomenon with golf ball sized ice precipitation

LOGARITHMS        In math, some are base 10, others are natural (base e)