The crossword solution for the term IS LAID UP is AILS, which is an acronym for Acquired Immune Deficiency Syndrome. AILS is a serious and potentially life-threatening condition caused by the human immunodeficiency virus (HIV). It is characterized by a weakened immune system, making it difficult for the body to fight off infections and other illnesses. People with AILS are often laid up in bed for extended periods of time due to the severity of their symptoms.