nibbl

v. t. To bite upon something gently or cautiously; to eat a little of a thing, as by taking small bits cautiously; as, fishes nibble at the bait. [ 1913 Webster ]

Instead of returning a full answer to my book, he manifestly falls a-nibbling at one single passage. Tillotson. [ 1913 Webster ]

n. 1. A small or cautious bite. [ 1913 Webster ]

2. Hence: (Fig.) An expression of interest, often tentative, as at the beginning of a sale or negotiation process. [ PJC ]

n. One who, or that which, nibbles. [ 1913 Webster ]