Definition of catch someone with their pants (or trousers) down in English:

catch someone with their pants (or trousers) down

phrase

informal
  • Catch someone in an embarrassingly unprepared state.

    ‘it's a wonder the government hasn't been caught with its pants down’
    • ‘I could not believe the irony of the fact that for our one and only sighting of this most secretive of creatures I had been caught with my pants down, both metaphorically and literally speaking.’
    • ‘I mean, I knew the guy was a rotten apple, I knew what he was up to, and he still managed to catch me with my pants down because I simply didn't pay attention at the right time… ah, figuratively speaking, of course.’
    • ‘Arrogance and complacency has cost them dearly as the market has moved on and they have been caught with their pants down.’
    • ‘In Australia we were caught with our pants down when our nurses began to strike.’