Total amount of value extracted from the workforce. The increase in value in absolute terms occurs through a reduction in the hourly wage or an unpaid increase in working time.
Definition in “Capital”
I call absolute surplus value the one produced by the extension of the working day; on the contrary, to the one that arises from the reduction of the necessary working time and from the resulting change in the proportion of magnitude that mediates between both components of the working day, I call it relative surplus value.
Karl Marx. Capital, Book I, Chapter X, 1866.
Absolute surplus value in the class struggle
Increasing absolute surplus value for capital is simply paying less per hour worked by lowering salaries, signing contracts for 4 hours which then become full-time, doing unpaid overtime, etc.
The less a sector or a region is capitalized, the more urgent is, in the face of a crisis, the need to increase exploitation in absolute terms. That is why the tendencies towards pauperization are shown first in the countries with the weakest national capitals and within each country in the sectors with the most difficulties in capitalization.