WITH dict1 AS
(SELECT 'THIS' fr,
'THAT' t
FROM dual
UNION ALL
SELECT 'IS' fr,
'ARE' t
FROM dual
UNION ALL
SELECT 'EXAMPLE' fr,
'SOURCE' t
FROM dual
UNION ALL
SELECT 'STRING' fr,
'NUMBER' t
FROM dual),
table1 AS
(SELECT 'This is an example string' AS str,
1 AS sn
FROM dual
UNION ALL
SELECT 'This String has typ0s' AS str,
2 sn
FROM dual),
src AS
(SELECT regexp_substr(upper(s.str), '[^ ]+', 1, LEVEL) str2,
s.*,
rownum nn
FROM table1 s
CONNECT BY instr(TRIM(' ' FROM str), ' ', 1, LEVEL - 1) > 0
AND PRIOR sn = sn
AND PRIOR dbms_random.value IS NOT NULL),
repl AS
(SELECT nvl2(dict1.t, dict1.t, src.str2) lex,
sn,
nn
FROM src
LEFT JOIN dict1
ON dict1.fr = src.str2)
SELECT listagg(lex, ' ') within GROUP(ORDER BY nn),
sn
FROM repl
GROUP BY sn
It works now as you ask. Enjoy.
EDIT: FIDDLE with solution