kilter, n. [Cf. Gael. & Ir. cealt clothes, Gael. cealltair spear, castle, cause, Prov. E. kilter tool, instrument. Cf. Kilt.].
Regular order or proper condition. Same as kelter, but kilter is the more common spelling in the U. S. Used chiefly in the phrase out of kilter, meaning out of order or irregular in some manner. [1913 Webster]