In simple terms, "substantial reduction" means a big decrease or a significant lowering of something.
Sentences with «substantial reduction»
The table shows that retirement at age 62 results in substantial reductions in monthly benefits. (ssa.gov)
It also highlights the need for substantial reductions in greenhouse gas emissions. (scientificamerican.com)
Background: Several fast food companies have made commitments to reduce the levels of salt in the foods they serve, but technical issues are often cited as a barrier to achieving substantial reductions. (cmaj.ca)