Does the engine 'turn over'? This means if you turn the key to the start position, does the starter motor make the engine go round? If it goes round, that's what we mean by turning over. So an engine can turn over (go round) but not actually start (fire).
'Dead'. Be careful when using this term. As a rule this is taken as absolutely dead, that is nothing at all happens when you switch on the ignition. If the dashboard lights up, but the engine doesn't 'turn over' (see above) then it's not 'dead' as such. Probably safest not to use this at all.