"At all hours" is a phrase that refers to a period of time throughout the day and night. It means that something is happening or someone is available with no regard for time constraints. Synonyms for this phrase include "24/7" or "round the clock" which both indicate that something is happening all day and all night. Another synonym is "constantly" which suggests that something is happening continuously without any break. "Nonstop" and "uninterrupted" also provide similar connotations. "Day and night", "all day long", and "always" are other synonyms that highlight the unrestricted nature of activities occurring "at all hours".