An oar that is worked with great effort. / (chiefly US, figuratively, by extension) The part of a task that requires the greatest effort to achieve.

(American spelling) Alternative spelling of child labour

(American spelling) Work which one is compelled to perform against one's will, especially in a condition of involuntary servitude as a prisoner or slave.

(economics) The market consisting of the supply of unemployed workers in relation to the demand for them.

(US) Alternative spelling of labour force

(American spelling) Work done by hand or using basic tools rather than by machines; usually physically demanding but (sometimes derogatory) unskilled labor.

(Canada, US) A continuous association of wage-earners for the purpose of maintaining or improving the conditions of their employment; a trade union.

plural of labor union

(American spelling) Requiring a great deal of work, especially physical and manual effort versus capital.

(US), (Canada) The holiday marking the unofficial end of summer, held on the first Monday in September. / An annual holiday held on May 1 to celebrate the economic and social achievements of workers.