pill. n. 1. (Pharmacology) a small spherical or ovoid mass of a medicinal substance, intended to be swallowed whole. 2. (Medicine) the pill (sometimes capital) an oral contraceptive. 3. something unpleasant that must be endured (esp in the phrase bitter pill to swallow). 4. a ball or disc. 5. a small ball of matted fibres that forms on the surface of a fabric through rubbing.
Fill your jars, while still hot place a waxed disc over the pickle, then a clear (cellophane) circle over the top of the jar, and secure with a rubber band. As anything with vinegar can get through the clear top it's best to put a metal lid as well, over the clear cover.
Hot pack your jars when it is indicated to do so in your recipe. Air could have been sealed in the jar because either the headspace was too large or the air bubbles were not removed: Be sure to use the headspace that is recommended in the recipe that you are using. Use a spatula or a bubble freer and slide it between the food and jar; press back on the food gently in order to release trapped air bubbles.