thru

less common spelling of through

Tho vs. Though and Thru vs. Through: Usage Guide

While never extremely common, tho and thru have a long history of occasional use as spelling variants of though and through. Their greatest popularity occurred in the late 19th and early 20th centuries, when their adoption was advocated by spelling reformers. Their current use occurs chiefly in informal writing (as in personal letters) and in some technical journals.

Kids Definition

thru

variant of through