17 of the Best Synonyms for ‘Poisonous’


By Dr Oliver Tearle

What’s the difference between a ‘poisonous’ snake and a ‘venomous’ one? Although these two words are often used interchangeably or synonymously, some distinction between them is also sometimes made: a poisonous creature is one that will harm you if you eat it, whereas a venomous animal is one that can bite or sting you, injecting its venom into your body.

This distinction is necessary if we are to get a sense of what words are synonymous with poisonous and which have a subtly different meaning. The following words can all, however, be used as synonyms for poisonous, albeit with some important caveats (which we’ll mention as we go).

Well, let’s start with VENOMOUS. Venom is poisonous fluid secreted by animals (especially snakes) in order to attack other creatures. The word venom is ultimately from the Latin venēnum, meaning a poison, potion, or drug. (Indeed, poison is from the Latin pōtiōn- or pōtiō, which gives us the word ‘potion’.)

Curiously, according to the Oxford English Dictionary (OED), the word ‘venomous’ was used figuratively (to mean ‘pernicious’ or ‘destructive’) before it was used literally, to describe a creature capable of secreting poison. But even by the fourteenth century, both the figurative and literal senses were firmly established.

TOXIC is a straightforward synonym for poisonous. Something which is toxic contains poison in some way. However, the word’s origins are more curious and surprising than either poisonous or venomous.

The word is from the Latin toxicum, which originally meant ‘poison for arrows’. The ancient Greek Τοξικόν meant ‘of or pertaining to the bow’, and originally it had nothing to do with poison at all. But because of poisoned arrows and darts, the association between poison and arrows led to the word toxicum being used to mean ‘poison for arrows’ and then, in more extended use, to mean ‘poison’ of all kinds. Indeed, another name for archery – the sport involving the shooting of an arrow from a bow – is toxophily, from the same Greek root.

Of course, something poisonous might not necessarily kill you. But when we use the word poisonous in its more general, extended sense to denote something corrupting or damaging, the association between poison and death becomes undeniable. And so words such as LETHAL, FATAL, DEADLY, and MORTAL, all meaning the same thing, can be employed as synonyms for poisonous, too.

Leaving deadliness (half) behind, the language of contagion and illness also infects the dialogue around poisonous things, so that, if we’re talking about a poisonous influence or poisonous attitudes, we can use such words as VIRULENT, INFECTIOUS, and CONTAGIOUS.

All three of these words refer to illnesses or viruses which are spread from one person to another, so if you’re trying to capture the sheer scale of a poisonous influence or effect, these words are especially useful.

NOXIOUS, meanwhile, is from the Latin noxius meaning ‘harmful’, or, indeed, ‘guilty’. It can denote something harmful, poisonous, or just unwholesome, so has a broader meaning than, say, toxic.

And talking of HARMFUL, there’s a whole series of synonyms for poisonous which pertain to harm or corruption. These include PERNICIOUS and CORRUPTING but also EVIL: someone who is a poisonous influence might well be an evil influence, as well as MALIGNANT, MALEVOLENT, or MALICIOUS.

All three of these words are from the Latin malus, meaning ‘bad’. All three words are often used to refer to people who have harmful or evil intentions or who do evil things, although malignant is also used in biology and medicine, such as when referring to a type of cancerous tumour. Given poison’s tendency to infect everything it comes into contact with, the implication is that malignant or malevolent behaviour infects all it touches.