The phrase "apply crudely" is defined as using a rough and unsophisticated approach to something. There are several synonyms for the phrase that can be used to convey a similar meaning. These include "apply roughly," "use clumsily," "employ ineptly," "utilize primitively," "execute crudely," and "implement unskilfully." These synonyms can be used depending on the context in which the phrase is used. It is essential to choose the right synonym that will accurately convey the intended meaning and help to provide clarity to the reader.