"Fiddle-de-dee" is an expression that denotes an insignificant, trivial thing or a dismissive response. Several synonyms can express the same sentiments, including "pish-posh," "baloney," "rubbish," "nonsense," and "poppycock." These words are commonly used in informal settings to signal the speaker's disbelief or criticism of a statement or situation. Other words that might also convey a dismissive tone include "hogwash," "malarkey," "twaddle," and "flapdoodle." Depending on the context, these synonyms might be considered mild or slightly impolite, so choosing the right word depends on the relationship between the speaker and the listener and the situation at hand.