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2.
adjective

1 - having a harmful effect, eg to health

2 - the panicky paranoid state of mind which inspires one to go through old emails, texts, etc, deleting anything which may be vaguely incriminating
I found my girlfriend going through my phone, but it's ok cos I got a bit deleterious last week and wiped those drunk text messages to my ex from my outbox
by jgrooves September 05, 2010
 
1.
Causing harm or damage.
Divorce is assumed to have deleterious effects on children.
by Kate Hines January 22, 2008