Cyclical Sector: A sector that is sensitive to economic fluctuations and tends to exhibit more radical swings, correlated with the overall business cycle, such that revenues are generally higher in periods of economic prosperity and expansion, lower in periods of economic downturn and contraction. There are nine sectors considered cyclical: basic materials, capital goods, communications, consumer cyclical, energy, financial, health care, technology and transportation.

Sources: Investopedia, About.com, Mindxpansion