Any mail or letters that are not welcome or solicited and typically sent in bulk; especially mail of a commercial nature such as advertising circulars and form letters.

(genetics) Any portion of the DNA sequence of a chromosome or a genome with no apparent function.

(finance) A bond (an instrument of debt) which is considered below "investment grade" due to a significant risk of default by the issuer. The interest rate is higher in order to compensate holders for that risk.

(informal) Space debris.

Alternative form of junk sick

(slang) Experiencing the nausea sometimes suffered by the user of a narcotic the following day, or after the effects of the drug begin to wear off, often with flulike symptoms.

(uncountable, derogatory) Assertions that have the appearance, but not the actuality, of scientific support.

plural of junk science

(countable, derogatory) A form of academic conference which is run for other than academic purposes and which does not meet normal academic standards.

(UK, US, informal) A worthless or malfunctioning piece of mechanical or electrical equipment.