tilly /ˈtɪli/adjective 1noun 2forms 4 adjective1 •Containing till (unsorted glacial sediment). noun2 •(Ireland) An extra product given to a customer at no additional charge; a lagniappe.He watched her pour into the measure and thence into the jug rich white milk, not hers. […] She poured again a measureful and a tilly. — 1922 •(UK) A small open-backed truck.After a fortnight's careful nursing my leg healed and I was packed off in a tilly (utility truck) with my kit-bag to join my comrades at Fairmilehead. — 1978 formsTillies · tillies · more tilly · most tilly