a. Geol. [f. FLUID sb. + -AL.] Of or resembling a fluid: (see quots.).
1879. Dana, Man. Geol. (ed. 3), 65. Igneous rocks sometimes exhibit under the microscope a fluidal texture; that is, the material, when examined in sections, shows wavy lines or bands, which are evidence of a former fluid state, and of movement or flowing when in that state.
1893. Geikie, Geol. (ed. 3), 100. This structure [streaked] conspicuously shown by the lines of flow in vitreous rocks (flow-structure, fluxion-structure, fluidal-structure) is less marked where the materials have assumed definite crystalline forms.
