Off form is a phrase commonly used to describe a state of inaptitude or poor performance. However, in order to avoid repetition, it may be useful to have some synonymous phrases on hand. One possibility could be "below par," which carries a similar connotation of a performance that is lacking or insufficient. Another phrase that could be used is "out of sorts," which refers to a state of disorientation or feeling disorganized. Alternatively, "subpar" and "underwhelming" may be used to convey a less than stellar performance. These synonyms can be especially useful in avoiding repetitive language and creating a more varied and engaging writing style.