indiscernible [ˌɪndɪˈsɜ:rnəbl]

例句:

• The transition was almost indiscernible.
  那转变几乎不能察觉.
  
• The path was altogether indiscernible in the murky darkness which surrounded them.
  来自Sir W. Scott
• Barwick's vocals are weightless, near-indiscernible things that colour the acoustic strums of Negro.
  来自BBC
• With no fluorescent clothing, she was indiscernible in the four mirrors focused on the lorry's blind side.
  来自THETIMES