Entry 1 sense Webster, 1913 Accelerometer /ăk-sĕlˌ-ẽr-äm'-ət-ẽr/ · Ac·cel·er·om·e·ter · IPA /ækˌsɛl.əˈɹɑ.mə.tɚ/ 01 n. An apparatus for measuring the velocity imparted by gunpowder. 1. An apparatus for measuring the velocity imparted by gunpowder.