(IE; I never use the word "chip" to mean crisps or fries - I will instead use "Crisps", despite it being british, and fries, despite it being American; in order to avoid ambiguity.)
The more difficult one is "pants", I would say underwear or trousers.
It's interesting how I only notice how much it's contrasted when I go back to the UK and hear others, I notice people using words that I've put a mental "X" on, and its only then that I realise that I've put the mental "X" on the word... because it no longer feels natural to hear it.