Python Pandas Dataframe search text in the cells

This a way:

def find_elements(row):
    for element in df2.Data.unique():
        if row.Column2.str.contains(element):
            return element

df3 = df1.copy()
df3["Column3"] = df3.apply(find_elements, axis=1)

That should work, of cource, you can find other way to do it.

Edit : As mentioned by @vb_rises if several word are in the same sentence, the function will only return the first match.

If you want to get all possible occurencies you can use the following function. Keep in mind that you should deal with lowercase too.

lst = [l.lower() for l in df2["DATA"].unique().to_list()]

def fun(x):
    x = x["Column2"].lower()
    return [l.capitalize() for l in lst if l in x]

df1["Column3"] = df1.apply(fun, axis=1)

Use Series.apply + lambda function with list comprehension to the case there is more than one word per cell:

df1['Column3']=df1['Column2'].apply(lambda x: [word  for word in df2['DATA'] if word.upper() in x.upper()])
print(df1)

   Column1                                        Column2   Column3
0   546852                     Lorem,ipsum,dolor,sit,amet   [Lorem]
1   248597  Amet,luctus,venenatis,lectus,magna,fringilla.  [Lectus]
2   842457          Neque,egestas,congue,quisque,egestas.  [Congue]
3     8465                   Amet,luctus,venenatis,lectus  [Lectus]
4      648                           Neque,egestas,congue  [Congue]
5       55                              Lorem,ipsum,dolor   [Lorem]