Hold up under refers to the ability to withstand pressure or adversity. Some synonyms for hold up under include endure, withstand, bear, sustain, and tolerate. These words suggest a sense of resilience and strength when facing challenges. Endure implies a willingness to persevere through hardship, while withstand suggests a greater sense of physical resistance to pressure. Bear emphasizes the idea of carrying a burden with patience and fortitude, whereas sustain implies the ability to maintain strength or stability. Tolerate suggests a certain level of endurance, but also a willingness to put up with difficulty for a time. Overall, these synonyms emphasize the importance of perseverance and a stalwart attitude in the face of adversity.