Lanefan
Victoria Rules
First off, the term "trip" defines a fairly narrow action-result sequence, most notably that the thing tripped almost always falls in the direction of whatever is tripping it (i.e. if tripped from behind you fall backwards, if from in front you fall forwards, etc.). Using a shield to tip something over such that it falls away from you is not tripping it.That's only one possibility. I could go on for pages with ways in which it could be momentarily squashed (long enough to have whatever disadvantages "trip" gives before it rights itself) by a character using a method that resembles the many ways in which someone could use an action that resembles "tripping". (Put your shield under it and LIFT). It's all dependent on 1) Who's doing the tripping and what do they have; 2) What's the terrain/room like; 3) What previously happened to the cube (did someone just firebolt it? Is there anyone inside? Did it just shuffle forward?, etc, etc).
Had the designers meant "knock over" I think they'd have used that term.
Never mind that were it me that shield would immediately have to save vs acid damage.....