axilla
noun
ax·il·la ag-ˈzi-lə 
ak-ˈsi-
ak-ˈsi- plural axillae ag-ˈzi-(ˌ)lē
-ˌlī
or axillas : the cavity beneath the junction of a forelimb and the body
especially : armpit
Example Sentences
Recent Examples on the Web The vaccine may enlarge the lymph nodes in the axilla, or armpit, according to Parkinson. 
Becky Jacobs, The Salt Lake Tribune, 19 Dec. 2021 In one woman, the swelling would be seen only in the left axilla. Melissa Healy, Los Angeles Times, 12 May 2021 After all, the vaccine is supposed to elicit an immune response and typically injected into your upper arm, which is close to your axilla. Bruce Y. Lee, Forbes, 3 Mar. 2021
Becky Jacobs, The Salt Lake Tribune, 19 Dec. 2021 In one woman, the swelling would be seen only in the left axilla. Melissa Healy, Los Angeles Times, 12 May 2021 After all, the vaccine is supposed to elicit an immune response and typically injected into your upper arm, which is close to your axilla. Bruce Y. Lee, Forbes, 3 Mar. 2021 Word History
Etymology
borrowed from Latin, diminutive of āla "armpit, upper arm, wing, axil" (axilla < *aksl̥-lā < *aksl-elā < *aksl- + *-el-, diminutive suffix) — more at ala
Note: Latin axilla is marginally attested in classical Latin, in a remark made by Cicero on its relation to āla ("fuga litterae vastioris" - "by the loss of an unwieldy letter"; Orator 153) and in a Greek glossary of Latin words. The usual Late Latin form is a metathesized ascilla or ascella, taken to mean "armpit," the sense "wing" being restricted to āla; from ascella descend Romance forms as Italian ascella "armpit," French aisselle.
First Known Use
1616, in the meaning defined above
Medical Definition
axilla
noun
ax·il·la ag-ˈzil-ə ak-ˈsil-
ak-ˈsil- plural axillae -(ˌ)ē, -ˌī or axillas
or axillas : the cavity beneath the junction of the arm or anterior appendage and shoulder or shoulder girdle containing the axillary artery and vein, a part of the brachial plexus of nerves, many lymph nodes, and fat and areolar tissue
especially : armpit