1.Lit. to tighten one's belt a bit. (Probably because one has not eaten recently or because one has lost weight.) He pulled his belt in a notch and smiled at his success at losing weight. He took in his belt a notch and wished he had something to eat.
2.Fig. to reduce expenditures; to live or operate a business more economically. (As if one were going to have to eat less.) They had to take their belts in a notch budgetarily speaking. The people at city hall will have to pull in their belts a notch unless they want to raise taxes.