A "blank mind" refers to a state of mental emptiness or absence of thought. Synonyms for this phrase include "empty-headed," "vacant," "thoughtless," "unthinking," "mindless," "inattentive," "absent-minded," "unaware," "unconscious," "vapid," and "numb." These words are often used to describe a person who seems to be in a daze or lacks mental focus and concentration. Alternatively, the phrase "mental block" can also be used to describe a similar state of mind, in which a person cannot think of anything else, despite repeated attempts to do so.