decuman
An extraordinarily large billow.
obsolete
Looking up suddenly, I found mine eyes / Confronted with the minster's vast repose. / Silent and gray as forest-leaguered cliff / Left inland by the ocean's slow retreat, / […] / Remembering shocks of surf that clomb and fell, / Spume-sliding down the baffled decuman, […]
Where it comes from
From Latin decumānus (“of the tenth, and by metonymy, large”), from decem (“ten”).
Adapted from the Wiktionary entry decuman (CC BY-SA 4.0).