Definition of lapilli in US English:


plural noun

  • Rock fragments ejected from a volcano.

    • ‘We infer that the framework through which transport took place consists of lapilli lodged within elutriation networks similar to those observed in the field (vertical ‘pipes’ having elongated sheet-like forms in three dimensions).’
    • ‘Mount Vesuvius' eruption buried the ancient Roman city of Pompeii in volcanic ash and lapilli, preserving it in its current ghost-town-like state.’
    • ‘Atmospheric aggregates include: fine particles lodged in the vesicles of larger grains; ash clots and flakes bound by electrostatic forces; accretionary lapilli, pellets or mud-drops formed by wet particle adhesion.’
    • ‘We thought they might be lapilli - little volcanic hailstones that form when you have an eruption of volcanic ash and it coagulates and falls out.’
    • ‘Some matrix ash samples were also analysed to ensure that the complete geochemical range could be assessed, and where lapilli were not available.’


Mid 18th century (in the general sense ‘stones, pebbles’): via Italian from Latin, plural of lapillus, diminutive of lapis ‘stone’.