When it comes to describing a secretive or illicit method, there are a plethora of synonyms to choose from. Some words that may come to mind include clandestine, covert, surreptitious, hidden, underhanded, sneaky, furtive, stealthy, and cloak-and-dagger. Each of these words suggests a certain level of secrecy or deception, whether it's the subtle approach of being furtive or the more dramatic flair of being cloak-and-dagger. Ultimately, the choice of synonym will depend on the context and level of seriousness surrounding the situation, but one thing is certain: there's no shortage of words to choose from when it comes to describing a secretive or illicit method.