(biochemistry) Initialism of haptoglobin-related protein.

(pathology) Initialism of holoprosencephaly.

(signal processing) Initialism of high-pass filter.

(computing) Initialism of High Performance File System, a file system used by the OS/2 operating system and early versions of Windows NT.

(Internet) Initialism of HTTP Public Key Pinning.

(uncountable) Abbreviation of hydrogen peroxide gas plasma.

Initialism of histrionic personality disorder.

Initialism of hypothalamic-pituitary-adrenal.

(UK, historical) Initialism of Health Protection Agency.

(analytical chemistry) high-performance liquid chromatography or high-pressure liquid chromatography