CEDICT
short for 七言律詩／七言律诗 (qīyán lǜshī) (an eight-line poem with seven characters to a line and a strict tonal pattern and rhyme scheme; septasyllabic (or seven-syllable) regulated verse)
Wiktionary
一种诗体。七言律诗的简称。每首八句，每句七字，三、四句及五、六句对仗，平仄有一定格式。
重編國語辭典
七言律诗／七言律诗的简称。
維基詞典