"The first heart sound or "lub" results from closure of the tricuspid and mitral valves. It is a rather low-pitched and a relatively long sound which, as indicated in, represents the beginning of ventricular systole.
The second heart sound, or "dub," marks the beginning of ventricular diastole. It is produced by closure of the aortic and pulmonary (pulmonic) semilunar vanes when the intraventricular pressure begins to fall. This "dub" sound is typically heard as a sharp snap because the semilunar valves tend to close much more rapidly than the AV valves. Because diastole occupies more time than systole, a brief pause occurs after the second heart sound when the heart is beating at a normal rate. Therefore, the pattern that one hears is one of: "lub-dub" pause, "lub-dub" pause, and so on.
Sometimes, especially in young normal individuals, a third heart sound can be heard. This sound is produced by the very rapid influx of blood into the partially filled ventricle. It is typically very faint and as such difficult to hear"
Reference: http://www.jdaross.cwc.net/normal_heart_sounds.htm
The second heart sound, or "dub," marks the beginning of ventricular diastole. It is produced by closure of the aortic and pulmonary (pulmonic) semilunar vanes when the intraventricular pressure begins to fall. This "dub" sound is typically heard as a sharp snap because the semilunar valves tend to close much more rapidly than the AV valves. Because diastole occupies more time than systole, a brief pause occurs after the second heart sound when the heart is beating at a normal rate. Therefore, the pattern that one hears is one of: "lub-dub" pause, "lub-dub" pause, and so on.
Sometimes, especially in young normal individuals, a third heart sound can be heard. This sound is produced by the very rapid influx of blood into the partially filled ventricle. It is typically very faint and as such difficult to hear"
Reference: http://www.jdaross.cwc.net/normal_heart_sounds.htm
by Lub Dub April 4, 2009
Get the Lub Dubmug. 
When something is extremely hard but you want to sound like it was easy for someone as smart as you.
by Nobody01100001 May 22, 2019
Get the Ez Dubsmug. a twenty dollar sack of marijuana. or a "dub". also can refer to other more hard twenty dollar sacks of drugs but is most comonly used for weed
by juggaloOG September 23, 2005
Get the dub sacmug. by frnk070 November 9, 2011
Get the wet dubmug. In basketball, a performance in which a player accumulates a double-digit number total in three of five statistical categories—points, rebounds, assists, steals, and blocked shots—in a game---a feat frequently accomplished by members of the OKC Thunder.
by Uncle J MythMan November 29, 2016
Get the trip dubmug.