From Longman Dictionary of Contemporary Englishplough something ↔ back phrasal verbMONEYto use money that you have earned from a business to make the business bigger and more successful into Companies can plough back their profits into new equipment. → plough→ See Verb table
Examples from the Corpus
plough back• In the near term, it does not intend to pay any dividends, instead ploughing all profits back.• They were not ones for put-ring their hand to the plough then looking back.• The immediate alternative to burning is to plough the straw back in, but that can be prohibitively expensive.• For the first four years I didn't take a wage and ploughed everything back into the business.• Seth had ploughed into the back of another van, earning himself a broken nose and twenty-five stitches in his face.• It appears their chair had ploughed into the back of another. 