Where a poem makes reference to another poem or text. For example, the 14th line of The Prelude by William Wordsworth 'The earth was all before me' alludes to one of the final lines of Paradise Lost by John Milton 'The world was all before them'. Paradise Lost, in turn, alludes to the story of Adam and Eve in Genesis.
Beta-blockers are drugs that bind to beta-adrenoceptors and thereby block the binding of norepinephrine and epinephrine to these receptors. This inhibits normal sympathetic effects that act through these receptors. Therefore, beta-blockers are sympatholytic drugs.
Definition of beta-blocker : any of a class of drugs (such as propranolol) that decrease the rate and force of heart contractions and lower high blood pressure by blocking the activity of beta-receptors