"Big smile tulip" is a descriptive phrase that may bring to mind a number of synonyms, depending on the desired connotation. For example, if we're aiming for a simile, we might think of "wide-grinning tulip" or "grinning like a tulip." Alternately, if we're looking for something that emphasizes the size of the bloom, we might consider "giant tulip with a grin" or "oversized smiling tulip." Other possibilities might include "jovial tulip," "happy tulip," or "smiling springtime bloom." Ultimately, the key is to find a synonym that captures the essence of the tulip's expression and conveys the desired tone of the text.