an interferometer consisting of two glass plates that reflect approximately half of each ray of light incident upon them and that are separated by a small, fixed distance: used to compare wavelengths and to study atomic spectra.
Origin: 1900–05; < French; Middle French estalon standard, derivative of Old French estal place < Germanic; see stall1
a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison.
an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.
a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison.
a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question.
physics a device used in spectroscopy to measure wavelengths by interference effects produced by multiple reflections between parallel half-silvered glass or quartz plates
[C20: French étalon a fixed standard of weights and measures, from Old French estalon; see also stallion]