Definition of by the seat of one's pants in US English:

by the seat of one's pants

phrase

informal
  • By instinct rather than logic or knowledge.

    • ‘It sounds like the orchestra is playing by the seat of their pants.’
    • ‘The rest of the trip will be conducted by the seat of our pants.’
    • ‘From now on we will not be a disorganized rabble fighting by the seat of our pants.’
    • ‘The steering is utterly lifeless, which means you have to steer by sight rather than by the seat of your pants.’
    • ‘I don't like playing music unless it's by the seat of your pants.’
    • ‘Once aviation became routine, the landing strips were refined and smoothed, but those first fliers had to land by the seat of their pants.’
    • ‘Often you find yourself operating by the seat of your pants, with no real idea of what you are doing or where the business is going.’
    • ‘I haven't heard playing of this intensity since Pablo Casals conducted Mozart where his orchestra, too, played by the seat of their pants.’
    • ‘But wars never proceed according to plan; they are always fought by the seat of one's pants, through constant improvisation.’
    • ‘I, on the other hand, play by the seat of my pants, improvising from the chords and syncopating most every rhythm with a lazy roadhouse beat.’