Definition of half seas over in US English:

half seas over

adjective

British
dated, informal
  • predicative Fairly drunk.

    ‘Winnie was half-seas-over’
    • ‘Everybody who saw the march, saw that the Champion of the Teetotallers was half seas over, and noted also that his brother, who made no hypocritical pretensions to extra temperance virtues, was dignified and sober.’
    • ‘But it pleased God before they came half seas over, to smite this young man with a grievous disease, of which he died in a desperate manner, and so was himself the first that was thrown overboard.’
    • ‘It's a place I've been known to frequent, and while I've never been afloat on a sailing boat I have frequently been half seas over.’
    • ‘But Alex Giannini brilliantly conveys Martin's comic cool, even down to his habit of rocking sideways while he sang as if half seas over.’
    intoxicated, inebriated, drunken, befuddled, incapable, tipsy, the worse for drink, under the influence, maudlin
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Pronunciation

half seas over

/haf sēz ˈōvər/