Premine : Coins were given out before mining started. That means basically in the genesis block a certain amount of coins were distributed to accounts when the chain started.
In PoS coins, this is typically a 100% premine as all the coins are created at block 0. An popular example of this is NXT.
credits : SomethingElse
Instamine / Fastmine : is different and also has a much broader definition. That is when a cryptocurrency in its early hours / days / period due to either accidental Instamine (Dash) or intentional crippling of mining software (Monero) or 1 person / group through early mining ending up with a large number of coins (Bitcoin / Satoshi 1 million BTC), delivers a lot of coins in a select few hands.
And now,
according to this account at least, we need to add
Giftmined where >50% of the entire network hashpower is gifted to a couple of individuals for a couple of months to turn them into millionaires by crippling the official code with ELNs (endless loops of nonsense).
The joys of early-day crypto
