The phrase "without reason" is often used to convey the absence of any logical or justifiable cause for a particular action or behavior. Other words that can be used as synonyms for this expression include "unreasonably," "unjustifiably," "irrationally," "senselessly," "pointlessly," "baselessly," "groundlessly," "illogically," and "absurdly." Each of these words conveys a similar meaning, and can be used in a variety of contexts to describe situations where there is no discernible justification or explanation for a particular action or outcome. Whether used in writing or conversation, these synonyms can help to add variety and nuance to your language, making your writing or speaking more engaging and effective.