strictly speaking, is a sail above the fore-royal, the main-royal, or the mizzen-royal, more frequently called “sky-scrapers.” In general parlance any top-sail is so called.
“Dashed by the strange wind's sport, we were sunk deep in the green
sea's trough; and before we could utter an ejaculatory prayer, were
upheaved upon the crown of some fantastic surge, peering our
sky-rakers into the azure vault of heaven.” —
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894