A slimy, desperate, perverted old man who seeks younger, more vulnerable mates. A dirty, loser man. The male equivalent of a cougar.
In nature, elephant seals have harums, in which one alpha male denies all other males access to the group. The non-alpha males are known to chill around the group, waiting to mount any young seal who strays from the pack.
"Ewww, Betty! The elephant seal at 3 o'clock is totally checking you out!"
"OMG! Jane is dating a total elephant seal. He's old enough to be her great-grandfather."