WordNet sense 1 (a period during the 1930s when there was a worldwide economic depression and mass unemployment):

Great Depression

WordNet sense 2 (an air mass of lower pressure; often brings precipitation):

low

WordNet sense 3 (a long-term economic state characterized by unemployment and low prices and low levels of trade and investment):

slump, economic crisis

WordNet sense 4 (a state of depression and anhedonia so severe as to require clinical intervention):

depressive disorder, clinical depression

WordNet sense 5 (a concavity in a surface produced by pressing):

impression, imprint, imprint

WordNet sense 6 (a sunken or depressed geological formation):

natural depression