The antonyms for the phrase 'read swiftly' are numerous, but the most common ones include - read slowly, read carefully, read attentively, peruse, scrutinize, examine, delve into, study, analyze, and contemplate. Reading slowly or carefully is often necessary when dealing with complex material that requires close attention. Perusing text, scrutinizing a document, examining a report or delving into the details of a study all imply a more thoughtful, thorough approach to reading. In some cases, it may be necessary to study or analyze a text in order to fully comprehend its meaning. Taking time to contemplate the words on a page can also yield a deeper understanding of the material.