The Vietnamese word "bí đái" refers to a condition commonly known as "urine retention." This means that a person is unable to urinate when they feel the need to do so. It can be uncomfortable and sometimes painful if it occurs for a prolonged period.
While "bí đái" primarily refers to urine retention, it can also be used in a colloquial sense to describe someone who is feeling very uncomfortable due to needing to urinate but being unable to find a place to do so.