1. [adj]  used of values and principles; not subject to change; steady; "undeviating loyalty"
2. [adj]  going directly ahead from one point to another without veering or turning aside; "some people see evolution as an undeviating upward march from simple organisms to the very complex"; "a straight and narrow tree-lined road unswerving across the lowlands"

UNDEVIATING is a 11 letter word that starts with U.