A sneaking suspicion is an intuition or feeling that something is not quite right. There are a variety of synonyms for this phrase such as a vague feeling, an inkling, a hunch or a gut instinct. Other synonyms include a premonition, presentiment, foreboding, intuition, and sixth sense. A suspicion can also be described as a feeling of mistrust or doubt, and may be called a skepticism, a misgiving or a distrust. On the other hand, a strong intuition may be termed as a conviction or a certainty. Using synonyms for "sneaking suspicion" can provide a more nuanced and descriptive way to communicate your intuition or gut feeling.