Lateral thinking is the practice of answering quizbowl questions by pulling out seemingly non-clue words from the question and combining them with knowledge about the target difficulty of the tournament or pet topics of the writer. For example, a question mentioning "women," "writing," and parts of a house may be on Virginia Woolf's A Room of One's Own, even if no actual clues about that book are recognizable. Conscious attempts to reward lateral thinking, and questions which inadvertently do so, are both hallmarks of bad quizbowl. References to the phrase "lateral thinking" or sarcastic after-tossup compliments such as "you figured it out" are common reactions to correct answers divined in this way rather than through actual knowledge.
Note that using lateral thinking clues very close to the end of a question in order to improve accessibility is not necessarily bad; using such clues early in the question (or for its entirety) is the problem.