A secondary predicate is a clausal adjunct or complement which attributes a quality or action to the subject or an object without employing a linking verb.
You are probably familiar with ordinary predicate complements (PCs) : constituents which occur as complements of linking verbs like be, become, seem and which describe or identify the subject. In these sentences the PC is in boldface:
John is our expert.
John has become fat.
John seems out of his depth.
Linking verbs do not take direct or indirect objects. But there are many verbs which take both an object and a PC. In cases of this sort many authorities call the PC a secondary complement or secondary predicate. Let's abbreviate it "SP". In these sentences the object is italicized and the SP is in boldface.
The board appointed Harold President and CEO.
I'm going to paint this room blue.
Please leave your essays on my desk. Most people consider him honest.
Note that in each of these the SP describes or identifies the object, just as they would if the SP were an ordinary PC joined to the object with a linking verb. This is usually the case when the verb is transitive.
Occasionally, however, the SP describes the subject.
Waiters served mead dressed as Vikings.
They played basketball in wheelchairs.
And it is also possible for a non-linking intransitive verb to take an SP. In these cases the SP describes the subject.
The moon shone white in the cloudless night.
Until quite recently people always swam naked.
The guard stood motionless and silent.
