BIP stands for –> Bitcoin Improvement Proposals

BIP0009:

# The ”’bit”’ determines which bit in the nVersion field of the block is to be used to signal the soft fork lock-in and activation. It is chosen from the set {0,1,2,…,28}.

# The ”’threshold”’ specifies how many blocks within a single retarget period (2016 blocks) must have the bit set before we lock in the deployment. The recommended value is 1916 (95%) for mainnet and 1512 (75%) for testnets.

# The ”’starttime”’ specifies a minimum median time past of a block at which the bit gains its meaning.

# The ”’timeout”’ specifies a time at which the deployment is considered failed. If the median time past of a block >= timeout and the soft fork has not yet locked in (including this block’s bit state), the deployment is considered failed on all descendants of the block.