What does "lethal" mean?

1. (deadly) able to cause death. 2. (very effective or dangerous) extremely successful or powerful, often in a way that defeats an opponent. 3. (a deadly gene) a version of a gene that causes an organism to die. 4. (a chemical compound) a type of solid alcohol found in certain oils and waxes.

lethal

adj. · n.

US //ˈɫiθəɫ// UK //lˈiːθəl// lethal

1 deadly (adj.)
B2 Upper Intermediate

able to cause death.

capable of causing death; fatal or mortal in effect.

Example

The snake's venom is lethal to small animals and humans.

Example

The laboratory confirmed that the chemical spill contained a lethal concentration of toxins, necessitating an immediate evacuation of the surrounding area.
- harmless
- safe
2 very effective or dangerous (adj.)
C1 Advanced Informal

extremely successful or powerful, often in a way that defeats an opponent.

highly effective or devastating in a figurative sense, particularly regarding skill or performance.

Example

The striker has a lethal shot that most goalkeepers cannot stop.

Example

Her lethal wit and sharp debating skills made her a formidable opponent in the courtroom.
- devastating
- potent
- weak
- ineffective

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3 a deadly gene (n.)
C2 Proficiency Technical Science

a version of a gene that causes an organism to die.

an allele that causes the death of the organism that carries it, often before birth or maturity.

Example

The researchers studied how a specific lethal gene was passed down in the fruit flies.

Example

The presence of a homozygous lethal in the population resulted in a significant deviation from the expected Mendelian ratios among the surviving offspring.
- lethal allele
4 a chemical compound (n.)
C2 Proficiency Technical Science

a type of solid alcohol found in certain oils and waxes.

one of the higher alcohols of the paraffin series, typically obtained from spermaceti as a white crystalline solid.

Example

The chemist isolated the lethal from the wax sample for further testing.

Example

The structural analysis of the lethal revealed a long-chain aliphatic alcohol consistent with derivatives of spermaceti.

Etymology 1

Learned borrowing from Latin lētālis (“deadly, mortal, fatal”), improperly written lēthālis, from lētum (“death”), improperly written as lēthum, from a supposed connection with Ancient Greek λήθη (lḗthē, “oblivion, forgetfulness”).

Etymology 2

Abbreviation of “lauric acid ethereal salt”, so called because it occurs in the ethereal salt of lauric acid.