Which of the following best describes 'encroach'?

The term 'encroach' is best described as advancing beyond the usual or proper limits. This word carries a connotation of gradual or subtle intrusion into an area where one does not have rightful authority or permission. It is often used in contexts such as land use, where one party may begin to use land or resources belonging to another, or in discussions of personal boundaries, where someone may infringe upon another's space or rights.

The other choices reflect different actions or states that do not align with the meaning of 'encroach.' For instance, to retreat means to withdraw from a position, which is opposite of advancing. Coexisting peacefully suggests a harmonious relationship without conflict, which does not imply any sort of intrusion. Lastly, communicating openly refers to the sharing of information or feelings, which is unrelated to the concept of encroachment. Therefore, 'encroach' encapsulates the idea of pushing boundaries, making the first description the most accurate.