(obsolete,slang) To mount sexually; also, to have an erection.
1590, Edmund Spenser, The Faerie Queene, III.x:
his louely wife emongst them lay, / Embraced of a Satyre rough and rude, / Who all the night did minde his ioyous play: / Nine times he heard him come aloft ere day, / That all his hart with gealosie did swell; / But yet that nights ensample did bewray, / That not for nought his wife them loued so well, / When one so oft a night did ring his matins bell.
1633, James Shirley, The Witty Fair One, IV.iv:
Fowler: I must kiss her:–(kisses her) – thou hast a down lip, and dost twang it handsomely; now to the business.
Penelope: This is not all I look for.
Fowler (aside): She will not tempt me to come aloft, will she?