This is the 2071st most frequent German word.
stellvertretende
"Stellvertretende" means "deputy" or "acting" in English, referring to someone or something serving as a representative or substitute.
In this sentence, 'stellvertretende' is used as an adjective describing the role of the 'Leiter' (leader), indicating that the person substitutes or acts on behalf of someone with the primary responsibility.
Ich bin der stellvertretende Leiter der Abteilung.
I am the deputy head of the department.
Here, 'stellvertretende' functions as an adjective modifying 'Vorsitzende' (chairwoman), specifying that the chairwoman is acting as a substitute for someone else.
Die stellvertretende Vorsitzende hielt die Rede.
The deputy chairwoman gave the speech.
In this instance, 'stellvertretend' is used adverbially to show that the action (assuming responsibility) is being done in place of or on behalf of another.