When searching for synonyms for the phrase "tight with," several options come to mind. First, we have "close with," which implies a strong bond or connection between two individuals. Other alternatives include "intimate with," "friendly with," and "fond of," all of which suggest a warm relationship between the parties involved. Additionally, we could use "allied with," "aligned with," or "partnered with," indicating a more formal or professional relationship. Finally, "chummy with," "bosom buddies with," and "thick as thieves with" are all casual, colloquial phrases that convey a sense of comfort and familiarity.