lamb·da / ˈlamdə/ • n. the eleventh letter of the Greek alphabet (Λ, λ), transliterated as ‘l.’ ∎  (Lambda) [followed by Latin genitive] Astron. the eleventh star in a constellation: Lambda Tauri. ∎  Biol. a type of bacteriophage virus used in genetic research: [as adj.] lambda phage. ∎  Anat. the point at the back of the skull where the parietal bones and the occipital bone meet. ∎  [as adj.] Biochem. denoting one of the two types of light polypeptide chain present in all immunoglobulin molecules (the other being kappa).• symb. ∎  (λ) wavelength. ∎  (λ) Astron. celestial longitude.

lambda (lam-dă) n. the point on the skull at which the lambdoidal and sagittal sutures meet.