Decent dictionary for offline use (Scrabble)

[UniFoxOs]

Having been fed up with SWMBO's continual challenging of my scrabble efforts (pitot, for example - she is not technically inclined) I have decided to try to get a dictionary we can use when travelling, so that we can have a definite reference. Ideally we want an electronic one that can be loaded on to her phone or pad (both Android). Trouble is that all the decent dictionary makers (Collins, for example) only seem to do paper editions, or an online edition, neither of which are particularly useful on holiday when you need to keep weight down (baggage allowance, not waistline) or are out of WIFI range.

Any ideas anyone? PDF would be OK, or other e-book forms that can be read on Android. Not a Google store app, though, I don't have good enough blood pressure to install them.

Cheers
UFO