Is it possible that it OTHER reflects off-duty work? I know some cities allow their officers to work off-duty but in uniform, and the places that want to use them have to pay the city directly instead of the officer.

I would have thought that would be overtime, thus in a different column

Overtime is usually time spent on the clock while "on-duty" - i.e. still performing their regular police duties, but hours over their standard workweek. Whereas an off-duty officer might be patrolling a bowling alley parking lot or high school football game - still in uniform, but not on "official police business".

I wonder if it would include something like injury compensation / some law enforcement-specific hazard pay... seems like it'd fit these large payouts.

The explanatory text says: "Gross pay includes overtime, bonuses, housing allowances, sick leave payout, vacation payout and multiple other forms of cash compensation"

So "Other" would be everything but base pay and overtime. Admittedly "multiple other forms of cash compensation" leaves lots of possiblities.

Well that leaves "bonuses, housing allowances, sick leave payout, vacation payout"

Most of the time sick leave payout and vacation payout is no more than the same day rate of a 'working' individual.

Thus it is hard to know why the OTHER column is bigger than the base salary.

Many government jobs allow you to accrue vacation and sick time without limit. If you're retiring and cash out 30 years of unused sick leave, that's a big lump payment.