| a hollow cylinder of thin glass with one end closed, used in chemical and biological experimentation and analysis. |

| test tube n. A clear, cylindrical glass tube usually open at one end and rounded at the other, used in laboratory experimentation. |
test tube n.
A clear, cylindrical glass tube usually open at one end and rounded at the other, used in laboratory experimentation.
test-tube adj.
Produced or cultivated in a test tube.
Conceived by or developed from fertilization in laboratory apparatus or by artificial insemination.