Webster's Revised Unabridged Dictionary · 1913

kilter

kilter (kil"tẽr) , noun

[Compare Gael. & Ir. cealt clothes, Gael. cealltair spear, castle, cause, Prov. English kilter tool, instrument. Compare 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.