α-addition (alpha-addition)

https://dx.doi.org/10.1351/goldbook.A00001
A chemical reaction resulting in a single reaction product from two or three reacting chemical species, with formation of two new chemical bonds to the same atom in one of the reactant molecular entities. The synonymous term 1/1/addition is also used. For example:
A00001-1
(This particular example can also be viewed as an insertion reaction). In inorganic chemistry such α-addition reactions, generally to a metallic central atom, are known as 'oxidative additions'. α-Addition is the reverse of α-elimination or 1/1/elimination.
See also: addition, elimination
Source:
PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1087