Non-defense discretionary spending. God, what a hideous term. The tip of the tongue takes a trip of ten steps and falls on its face at the -ding. In fact, it's such a revolting sequence of consonants, maybe that explains why politicians think we can cut it to the bone without anybody noticing.
Here is the case for noticing.
When government talks about spending as "investments," they're talking about this category, mostly. NNDS is everything that isn't Medicare, Medicaid, Social Security, defense, and mandatory spending on programs like unemployment benefits. It's everything that is infrastructure, education, training, disaster relief, environmental protections, international affairs, scientific research, and employee salaries.
In other words, it is the bulk of what we have historically called "Government." And in both President Obama and Rep. Paul Ryan's budgets, "Government" gets cut to a historic low as a share of, well, government. Here's the graph of non-defense discretionary spending ("Government") since 1970. After 2013, Obama's budget traces the orange line and Ryan's budget traces the blue line.