(inorganic chemistry) Any of the 14 radioactive elements of the periodic table that are positioned under the lanthanides, to which they have similar chemistry.

(chemistry) unbiunium / (chemistry) untriennium (dvi-lanthanum)

present participle of act out

plural of actinide

plural of acting

(pharmacology) Having a pharmaceutical effect principally in the short term.

(pharmacology) Having a pharmaceutical effect principally in the long term.

(rugby) a player who temporarily takes the scrum-half's place while the latter is unavailable due to being involved in the breakdown, having an injury, or having been sin-binned.

present participle of act up

(biochemistry) Any of several microfilament proteins that have a function in the attachment of actin fibres in muscle cells